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	$33.53	11.334%	$37.3303	$37.33	$37.35	$37.30
Purchase #2	$158.46	3.797%	$164.4767	$164.48	$164.50	$164.50
Purchase #3	$222.51	12.705%	$250.7799	$250.78	$250.80	$250.80
Purchase #4	$28.58	13.704%	$32.4966	$32.50	$32.50	$32.50
Purchase #5	$191.94	5.820%	$203.1109	$203.11	$203.10	$203.10
Purchase #6	$128.60	9.800%	$141.2028	$141.20	$141.20	$141.20
Purchase #7	$151.82	6.655%	$161.9236	$161.92	$161.90	$161.90
7 purchase totals =	$915.44		$991.3208	$991.32	$991.35	$991.30