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	$168.45	9.522%	$184.4898	$184.49	$184.50	$184.50
Purchase #2	$181.41	5.794%	$191.9209	$191.92	$191.90	$191.90
Purchase #3	$133.92	13.275%	$151.6979	$151.70	$151.70	$151.70
Purchase #4	$55.38	5.769%	$58.5749	$58.57	$58.55	$58.60
Purchase #5	$146.51	13.485%	$166.2669	$166.27	$166.25	$166.30
Purchase #6	$200.82	4.851%	$210.5618	$210.56	$210.55	$210.60
Purchase #7	$181.73	3.316%	$187.7562	$187.76	$187.75	$187.80
7 purchase totals =	$1,068.22		$1,151.2684	$1,151.27	$1,151.20	$1,151.40