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	$128.78	13.217%	$145.8009	$145.80	$145.80	$145.80
Purchase #2	$6.46	11.338%	$7.1924	$7.19	$7.20	$7.20
Purchase #3	$198.55	12.133%	$222.6401	$222.64	$222.65	$222.60
Purchase #4	$235.86	8.686%	$256.3468	$256.35	$256.35	$256.30
Purchase #5	$211.72	5.675%	$223.7351	$223.74	$223.75	$223.70
Purchase #6	$148.89	6.266%	$158.2194	$158.22	$158.20	$158.20
Purchase #7	$99.92	6.612%	$106.5267	$106.53	$106.55	$106.50
7 purchase totals =	$1,030.18		$1,120.4614	$1,120.47	$1,120.50	$1,120.30