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	$64.57	4.206%	$67.2858	$67.29	$67.30	$67.30
Purchase #2	$231.64	5.285%	$243.8822	$243.88	$243.90	$243.90
Purchase #3	$200.54	11.512%	$223.6262	$223.63	$223.65	$223.60
Purchase #4	$18.49	10.266%	$20.3882	$20.39	$20.40	$20.40
Purchase #5	$196.33	8.299%	$212.6234	$212.62	$212.60	$212.60
Purchase #6	$127.69	10.511%	$141.1115	$141.11	$141.10	$141.10
Purchase #7	$232.89	8.427%	$252.5156	$252.52	$252.50	$252.50
7 purchase totals =	$1,072.15		$1,161.4329	$1,161.44	$1,161.45	$1,161.40