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	$67.56	7.379%	$72.5453	$72.55	$72.55	$72.50
Purchase #2	$135.37	8.190%	$146.4568	$146.46	$146.45	$146.50
Purchase #3	$116.89	6.475%	$124.4586	$124.46	$124.45	$124.50
Purchase #4	$135.43	5.467%	$142.834	$142.83	$142.85	$142.80
Purchase #5	$7.57	12.168%	$8.4911	$8.49	$8.50	$8.50
Purchase #6	$100.65	7.261%	$107.9582	$107.96	$107.95	$108.00
Purchase #7	$136.72	9.784%	$150.0967	$150.10	$150.10	$150.10
7 purchase totals =	$700.19		$752.8407	$752.85	$752.85	$752.90