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	$146.33	11.227%	$162.7585	$162.76	$162.75	$162.80
Purchase #2	$33.97	4.846%	$35.6162	$35.62	$35.60	$35.60
Purchase #3	$216.73	5.297%	$228.2102	$228.21	$228.20	$228.20
Purchase #4	$165.45	8.232%	$179.0698	$179.07	$179.05	$179.10
Purchase #5	$196.63	12.491%	$221.1911	$221.19	$221.20	$221.20
Purchase #6	$104.64	9.800%	$114.8947	$114.89	$114.90	$114.90
Purchase #7	$167.71	13.300%	$190.0154	$190.02	$190.00	$190.00
7 purchase totals =	$1,031.46		$1,131.7559	$1,131.76	$1,131.70	$1,131.80