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	$99.74	11.777%	$111.4864	$111.49	$111.50	$111.50
Purchase #2	$150.75	11.751%	$168.4646	$168.46	$168.45	$168.50
Purchase #3	$203.55	6.380%	$216.5365	$216.54	$216.55	$216.50
Purchase #4	$47.63	5.774%	$50.3802	$50.38	$50.40	$50.40
Purchase #5	$148.70	4.603%	$155.5447	$155.54	$155.55	$155.50
Purchase #6	$67.34	12.456%	$75.7279	$75.73	$75.75	$75.70
Purchase #7	$113.29	10.430%	$125.1061	$125.11	$125.10	$125.10
7 purchase totals =	$831.00		$903.2464	$903.25	$903.30	$903.20