Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$233.29	13.265%	$264.2359	$264.24	$264.25	$264.20
Purchase #2	$174.98	9.142%	$190.9767	$190.98	$191.00	$191.00
Purchase #3	$216.64	13.279%	$245.4076	$245.41	$245.40	$245.40
Purchase #4	$100.87	11.412%	$112.3813	$112.38	$112.40	$112.40
Purchase #5	$127.74	12.418%	$143.6028	$143.60	$143.60	$143.60
Purchase #6	$248.79	8.506%	$269.9521	$269.95	$269.95	$270.00
Purchase #7	$214.47	13.166%	$242.7071	$242.71	$242.70	$242.70
7 purchase totals =	$1,316.78		$1,469.2635	$1,469.27	$1,469.30	$1,469.30