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	$158.64	4.304%	$165.4679	$165.47	$165.45	$165.50
Purchase #2	$101.56	12.138%	$113.8874	$113.89	$113.90	$113.90
Purchase #3	$63.76	11.792%	$71.2786	$71.28	$71.30	$71.30
Purchase #4	$145.70	6.709%	$155.475	$155.48	$155.50	$155.50
Purchase #5	$111.69	9.630%	$122.4457	$122.45	$122.45	$122.40
Purchase #6	$146.62	12.764%	$165.3346	$165.33	$165.35	$165.30
Purchase #7	$223.56	3.229%	$230.7788	$230.78	$230.80	$230.80
7 purchase totals =	$951.53		$1,024.6680	$1,024.68	$1,024.75	$1,024.70