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	$165.31	4.475%	$172.7076	$172.71	$172.70	$172.70
Purchase #2	$31.75	3.568%	$32.8828	$32.88	$32.90	$32.90
Purchase #3	$193.25	3.275%	$199.5789	$199.58	$199.60	$199.60
Purchase #4	$127.75	9.373%	$139.724	$139.72	$139.70	$139.70
Purchase #5	$72.89	9.854%	$80.0726	$80.07	$80.05	$80.10
Purchase #6	$66.51	5.118%	$69.914	$69.91	$69.90	$69.90
Purchase #7	$87.76	7.483%	$94.3271	$94.33	$94.35	$94.30
7 purchase totals =	$745.22		$789.2070	$789.20	$789.20	$789.20