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	$119.72	9.439%	$131.0204	$131.02	$131.00	$131.00
Purchase #2	$240.76	5.143%	$253.1423	$253.14	$253.15	$253.10
Purchase #3	$101.26	13.178%	$114.604	$114.60	$114.60	$114.60
Purchase #4	$141.53	11.602%	$157.9503	$157.95	$157.95	$158.00
Purchase #5	$186.27	12.508%	$209.5687	$209.57	$209.55	$209.60
Purchase #6	$41.44	8.213%	$44.8435	$44.84	$44.85	$44.80
Purchase #7	$189.78	5.536%	$200.2862	$200.29	$200.30	$200.30
7 purchase totals =	$1,020.76		$1,111.4154	$1,111.41	$1,111.40	$1,111.40