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	$113.28	13.181%	$128.2114	$128.21	$128.20	$128.20
Purchase #2	$161.72	6.325%	$171.9488	$171.95	$171.95	$171.90
Purchase #3	$138.29	5.788%	$146.2942	$146.29	$146.30	$146.30
Purchase #4	$65.74	8.408%	$71.2674	$71.27	$71.25	$71.30
Purchase #5	$165.31	11.793%	$184.805	$184.81	$184.80	$184.80
Purchase #6	$202.52	7.694%	$218.1019	$218.10	$218.10	$218.10
Purchase #7	$76.79	7.253%	$82.3596	$82.36	$82.35	$82.40
7 purchase totals =	$923.65		$1,002.9883	$1,002.99	$1,002.95	$1,003.00