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	$62.64	3.474%	$64.8161	$64.82	$64.80	$64.80
Purchase #2	$40.86	9.778%	$44.8553	$44.86	$44.85	$44.90
Purchase #3	$169.51	9.443%	$185.5168	$185.52	$185.50	$185.50
Purchase #4	$225.64	11.306%	$251.1509	$251.15	$251.15	$251.20
Purchase #5	$70.95	12.703%	$79.9628	$79.96	$79.95	$80.00
Purchase #6	$50.85	13.769%	$57.8515	$57.85	$57.85	$57.90
Purchase #7	$191.70	12.873%	$216.3775	$216.38	$216.40	$216.40
7 purchase totals =	$812.15		$900.5309	$900.54	$900.50	$900.70