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	$86.75	9.874%	$95.3157	$95.32	$95.30	$95.30
Purchase #2	$56.83	5.253%	$59.8153	$59.82	$59.80	$59.80
Purchase #3	$172.74	4.385%	$180.3146	$180.31	$180.30	$180.30
Purchase #4	$120.31	4.155%	$125.3089	$125.31	$125.30	$125.30
Purchase #5	$49.89	10.430%	$55.0935	$55.09	$55.10	$55.10
Purchase #6	$43.61	5.406%	$45.9676	$45.97	$45.95	$46.00
Purchase #7	$6.27	12.304%	$7.0415	$7.04	$7.05	$7.00
7 purchase totals =	$536.40		$568.8571	$568.86	$568.80	$568.80