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	$181.65	4.865%	$190.4873	$190.49	$190.50	$190.50
Purchase #2	$249.85	11.196%	$277.8232	$277.82	$277.80	$277.80
Purchase #3	$24.77	5.142%	$26.0437	$26.04	$26.05	$26.00
Purchase #4	$56.64	4.430%	$59.1492	$59.15	$59.15	$59.10
Purchase #5	$228.69	3.475%	$236.637	$236.64	$236.65	$236.60
Purchase #6	$202.42	10.611%	$223.8988	$223.90	$223.90	$223.90
Purchase #7	$122.54	11.107%	$136.1505	$136.15	$136.15	$136.20
7 purchase totals =	$1,066.56		$1,150.1897	$1,150.19	$1,150.20	$1,150.10