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	$219.41	4.432%	$229.1343	$229.13	$229.15	$229.10
Purchase #2	$121.72	11.684%	$135.9418	$135.94	$135.95	$135.90
Purchase #3	$153.69	7.609%	$165.3843	$165.38	$165.40	$165.40
Purchase #4	$166.54	11.382%	$185.4956	$185.50	$185.50	$185.50
Purchase #5	$18.44	11.246%	$20.5138	$20.51	$20.50	$20.50
Purchase #6	$38.43	5.758%	$40.6428	$40.64	$40.65	$40.60
Purchase #7	$144.55	3.697%	$149.894	$149.89	$149.90	$149.90
7 purchase totals =	$862.78		$927.0066	$926.99	$927.05	$926.90