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	$183.51	3.605%	$190.1255	$190.13	$190.15	$190.10
Purchase #2	$214.87	3.802%	$223.0394	$223.04	$223.05	$223.00
Purchase #3	$222.83	9.772%	$244.6049	$244.60	$244.60	$244.60
Purchase #4	$199.97	8.448%	$216.8635	$216.86	$216.85	$216.90
Purchase #5	$150.28	4.239%	$156.6504	$156.65	$156.65	$156.70
Purchase #6	$59.74	12.413%	$67.1555	$67.16	$67.15	$67.20
Purchase #7	$73.77	13.188%	$83.4988	$83.50	$83.50	$83.50
7 purchase totals =	$1,104.97		$1,181.9380	$1,181.94	$1,181.95	$1,182.00