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	$235.58	6.517%	$250.9327	$250.93	$250.95	$250.90
Purchase #2	$84.61	9.293%	$92.4728	$92.47	$92.45	$92.50
Purchase #3	$9.80	7.199%	$10.5055	$10.51	$10.50	$10.50
Purchase #4	$40.27	6.113%	$42.7317	$42.73	$42.75	$42.70
Purchase #5	$199.37	6.615%	$212.5583	$212.56	$212.55	$212.60
Purchase #6	$32.76	10.225%	$36.1097	$36.11	$36.10	$36.10
Purchase #7	$94.76	5.739%	$100.1983	$100.20	$100.20	$100.20
7 purchase totals =	$697.15		$745.5090	$745.51	$745.50	$745.50