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	$191.55	11.849%	$214.2468	$214.25	$214.25	$214.20
Purchase #2	$120.52	6.313%	$128.1284	$128.13	$128.15	$128.10
Purchase #3	$169.40	6.328%	$180.1196	$180.12	$180.10	$180.10
Purchase #4	$54.83	12.313%	$61.5812	$61.58	$61.60	$61.60
Purchase #5	$125.69	11.751%	$140.4598	$140.46	$140.45	$140.50
Purchase #6	$36.79	12.565%	$41.4127	$41.41	$41.40	$41.40
Purchase #7	$157.59	5.612%	$166.434	$166.43	$166.45	$166.40
7 purchase totals =	$856.37		$932.3825	$932.38	$932.40	$932.30