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	$195.89	13.222%	$221.7906	$221.79	$221.80	$221.80
Purchase #2	$62.80	9.317%	$68.6511	$68.65	$68.65	$68.70
Purchase #3	$210.37	10.465%	$232.3852	$232.39	$232.40	$232.40
Purchase #4	$107.77	3.497%	$111.5387	$111.54	$111.55	$111.50
Purchase #5	$32.55	13.818%	$37.0478	$37.05	$37.05	$37.00
Purchase #6	$184.94	12.741%	$208.5032	$208.50	$208.50	$208.50
Purchase #7	$212.72	5.112%	$223.5942	$223.59	$223.60	$223.60
7 purchase totals =	$1,007.04		$1,103.5108	$1,103.51	$1,103.55	$1,103.50