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	$88.28	4.827%	$92.5413	$92.54	$92.55	$92.50
Purchase #2	$116.82	11.596%	$130.3664	$130.37	$130.35	$130.40
Purchase #3	$159.40	12.311%	$179.0237	$179.02	$179.00	$179.00
Purchase #4	$222.93	9.507%	$244.124	$244.12	$244.10	$244.10
Purchase #5	$206.71	7.747%	$222.7238	$222.72	$222.70	$222.70
Purchase #6	$137.77	11.133%	$153.1079	$153.11	$153.10	$153.10
Purchase #7	$58.52	4.665%	$61.25	$61.25	$61.25	$61.30
7 purchase totals =	$990.43		$1,083.1371	$1,083.13	$1,083.05	$1,083.10