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	$143.61	5.472%	$151.4683	$151.47	$151.45	$151.50
Purchase #2	$28.86	4.590%	$30.1847	$30.18	$30.20	$30.20
Purchase #3	$38.90	8.299%	$42.1283	$42.13	$42.15	$42.10
Purchase #4	$20.50	12.509%	$23.0643	$23.06	$23.05	$23.10
Purchase #5	$79.46	4.363%	$82.9268	$82.93	$82.95	$82.90
Purchase #6	$200.84	11.175%	$223.2839	$223.28	$223.30	$223.30
Purchase #7	$157.69	7.218%	$169.0721	$169.07	$169.05	$169.10
7 purchase totals =	$669.86		$722.1284	$722.12	$722.15	$722.20