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	$148.61	13.732%	$169.0171	$169.02	$169.00	$169.00
Purchase #2	$201.49	10.614%	$222.8761	$222.88	$222.90	$222.90
Purchase #3	$176.31	12.218%	$197.8516	$197.85	$197.85	$197.90
Purchase #4	$116.59	13.533%	$132.3681	$132.37	$132.35	$132.40
Purchase #5	$150.74	10.660%	$166.8089	$166.81	$166.80	$166.80
Purchase #6	$55.42	10.109%	$61.0224	$61.02	$61.00	$61.00
Purchase #7	$85.53	9.314%	$93.4963	$93.50	$93.50	$93.50
7 purchase totals =	$934.69		$1,043.4405	$1,043.45	$1,043.40	$1,043.50