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	$189.48	12.160%	$212.5208	$212.52	$212.50	$212.50
Purchase #2	$181.58	5.476%	$191.5233	$191.52	$191.50	$191.50
Purchase #3	$96.79	13.453%	$109.8112	$109.81	$109.80	$109.80
Purchase #4	$37.33	8.172%	$40.3806	$40.38	$40.40	$40.40
Purchase #5	$10.57	5.467%	$11.1479	$11.15	$11.15	$11.10
Purchase #6	$105.79	8.611%	$114.8996	$114.90	$114.90	$114.90
Purchase #7	$41.29	13.637%	$46.9207	$46.92	$46.90	$46.90
7 purchase totals =	$662.83		$727.2041	$727.20	$727.15	$727.10