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	$241.77	9.702%	$265.2265	$265.23	$265.25	$265.20
Purchase #2	$111.89	12.160%	$125.4958	$125.50	$125.50	$125.50
Purchase #3	$54.90	8.821%	$59.7427	$59.74	$59.75	$59.70
Purchase #4	$32.65	11.488%	$36.4008	$36.40	$36.40	$36.40
Purchase #5	$171.65	4.165%	$178.7992	$178.80	$178.80	$178.80
Purchase #6	$179.27	4.727%	$187.7441	$187.74	$187.75	$187.70
Purchase #7	$214.53	11.276%	$238.7204	$238.72	$238.70	$238.70
7 purchase totals =	$1,006.66		$1,092.1295	$1,092.13	$1,092.15	$1,092.00