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	$213.65	4.146%	$222.5079	$222.51	$222.50	$222.50
Purchase #2	$248.64	6.157%	$263.9488	$263.95	$263.95	$263.90
Purchase #3	$48.63	5.787%	$51.4442	$51.44	$51.45	$51.40
Purchase #4	$212.56	13.131%	$240.4713	$240.47	$240.45	$240.50
Purchase #5	$121.84	13.425%	$138.197	$138.20	$138.20	$138.20
Purchase #6	$138.47	10.142%	$152.5136	$152.51	$152.50	$152.50
Purchase #7	$59.72	11.289%	$66.4618	$66.46	$66.45	$66.50
7 purchase totals =	$1,043.51		$1,135.5446	$1,135.54	$1,135.50	$1,135.50