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	$33.25	11.559%	$37.0934	$37.09	$37.10	$37.10
Purchase #2	$92.35	4.190%	$96.2195	$96.22	$96.20	$96.20
Purchase #3	$160.57	11.410%	$178.891	$178.89	$178.90	$178.90
Purchase #4	$243.72	4.796%	$255.4088	$255.41	$255.40	$255.40
Purchase #5	$242.47	12.707%	$273.2807	$273.28	$273.30	$273.30
Purchase #6	$221.66	12.245%	$248.8023	$248.80	$248.80	$248.80
Purchase #7	$148.74	11.252%	$165.4762	$165.48	$165.50	$165.50
7 purchase totals =	$1,142.76		$1,255.1719	$1,255.17	$1,255.20	$1,255.20