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	$95.31	10.346%	$105.1708	$105.17	$105.15	$105.20
Purchase #2	$141.68	4.222%	$147.6617	$147.66	$147.65	$147.70
Purchase #3	$175.51	7.565%	$188.7873	$188.79	$188.80	$188.80
Purchase #4	$127.62	10.213%	$140.6538	$140.65	$140.65	$140.70
Purchase #5	$110.31	11.729%	$123.2483	$123.25	$123.25	$123.20
Purchase #6	$97.56	7.160%	$104.5453	$104.55	$104.55	$104.50
Purchase #7	$55.33	10.140%	$60.9405	$60.94	$60.95	$60.90
7 purchase totals =	$803.32		$871.0077	$871.01	$871.00	$871.00