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	$206.62	12.795%	$233.057	$233.06	$233.05	$233.10
Purchase #2	$57.48	4.256%	$59.9263	$59.93	$59.95	$59.90
Purchase #3	$61.54	4.213%	$64.1327	$64.13	$64.15	$64.10
Purchase #4	$221.86	8.720%	$241.2062	$241.21	$241.20	$241.20
Purchase #5	$149.91	9.148%	$163.6238	$163.62	$163.60	$163.60
Purchase #6	$64.91	11.345%	$72.274	$72.27	$72.25	$72.30
Purchase #7	$228.85	9.523%	$250.6434	$250.64	$250.65	$250.60
7 purchase totals =	$991.17		$1,084.8634	$1,084.86	$1,084.85	$1,084.80