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	$210.96	10.227%	$232.5349	$232.53	$232.55	$232.50
Purchase #2	$95.77	9.872%	$105.2244	$105.22	$105.20	$105.20
Purchase #3	$33.95	6.195%	$36.0532	$36.05	$36.05	$36.10
Purchase #4	$144.57	6.240%	$153.5912	$153.59	$153.60	$153.60
Purchase #5	$179.75	7.791%	$193.7543	$193.75	$193.75	$193.80
Purchase #6	$55.68	6.186%	$59.1244	$59.12	$59.10	$59.10
Purchase #7	$70.57	11.325%	$78.5621	$78.56	$78.55	$78.60
7 purchase totals =	$791.25		$858.8445	$858.82	$858.80	$858.90