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	$215.29	10.495%	$237.8847	$237.88	$237.90	$237.90
Purchase #2	$152.46	9.635%	$167.1495	$167.15	$167.15	$167.10
Purchase #3	$79.95	11.399%	$89.0635	$89.06	$89.05	$89.10
Purchase #4	$134.57	8.413%	$145.8914	$145.89	$145.90	$145.90
Purchase #5	$61.47	9.344%	$67.2138	$67.21	$67.20	$67.20
Purchase #6	$138.70	10.655%	$153.4785	$153.48	$153.50	$153.50
Purchase #7	$226.79	13.207%	$256.7422	$256.74	$256.75	$256.70
7 purchase totals =	$1,009.23		$1,117.4236	$1,117.41	$1,117.45	$1,117.40