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	$128.92	13.678%	$146.5537	$146.55	$146.55	$146.60
Purchase #2	$155.89	9.826%	$171.2078	$171.21	$171.20	$171.20
Purchase #3	$54.82	7.823%	$59.1086	$59.11	$59.10	$59.10
Purchase #4	$215.84	4.470%	$225.488	$225.49	$225.50	$225.50
Purchase #5	$200.96	10.726%	$222.515	$222.52	$222.50	$222.50
Purchase #6	$7.81	4.715%	$8.1782	$8.18	$8.20	$8.20
Purchase #7	$202.60	9.843%	$222.5419	$222.54	$222.55	$222.50
7 purchase totals =	$966.84		$1,055.5932	$1,055.60	$1,055.60	$1,055.60