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	$75.49	3.234%	$77.9313	$77.93	$77.95	$77.90
Purchase #2	$225.69	10.517%	$249.4258	$249.43	$249.45	$249.40
Purchase #3	$66.28	7.869%	$71.4956	$71.50	$71.50	$71.50
Purchase #4	$77.30	10.643%	$85.527	$85.53	$85.55	$85.50
Purchase #5	$189.92	9.745%	$208.4277	$208.43	$208.45	$208.40
Purchase #6	$240.95	12.644%	$271.4157	$271.42	$271.40	$271.40
Purchase #7	$218.47	6.363%	$232.3712	$232.37	$232.35	$232.40
7 purchase totals =	$1,094.10		$1,196.5943	$1,196.61	$1,196.65	$1,196.50