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	$33.29	12.485%	$37.4463	$37.45	$37.45	$37.40
Purchase #2	$81.83	4.645%	$85.631	$85.63	$85.65	$85.60
Purchase #3	$90.38	5.465%	$95.3193	$95.32	$95.30	$95.30
Purchase #4	$131.89	8.590%	$143.2194	$143.22	$143.20	$143.20
Purchase #5	$102.36	7.561%	$110.0994	$110.10	$110.10	$110.10
Purchase #6	$250.58	7.538%	$269.4687	$269.47	$269.45	$269.50
Purchase #7	$18.94	11.649%	$21.1463	$21.15	$21.15	$21.10
7 purchase totals =	$709.27		$762.3304	$762.34	$762.30	$762.20