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	$62.46	7.323%	$67.0339	$67.03	$67.05	$67.00
Purchase #2	$59.34	3.861%	$61.6311	$61.63	$61.65	$61.60
Purchase #3	$90.94	13.617%	$103.3233	$103.32	$103.30	$103.30
Purchase #4	$205.74	5.379%	$216.8068	$216.81	$216.80	$216.80
Purchase #5	$98.61	12.638%	$111.0723	$111.07	$111.05	$111.10
Purchase #6	$167.50	9.104%	$182.7492	$182.75	$182.75	$182.70
Purchase #7	$124.90	4.324%	$130.3007	$130.30	$130.30	$130.30
7 purchase totals =	$809.49		$872.9173	$872.91	$872.90	$872.80