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	$41.64	8.730%	$45.2752	$45.28	$45.30	$45.30
Purchase #2	$151.38	6.244%	$160.8322	$160.83	$160.85	$160.80
Purchase #3	$237.73	13.495%	$269.8117	$269.81	$269.80	$269.80
Purchase #4	$168.64	6.422%	$179.4701	$179.47	$179.45	$179.50
Purchase #5	$96.63	4.327%	$100.8112	$100.81	$100.80	$100.80
Purchase #6	$197.97	8.130%	$214.065	$214.07	$214.05	$214.10
Purchase #7	$116.47	7.301%	$124.9735	$124.97	$124.95	$125.00
7 purchase totals =	$1,010.46		$1,095.2389	$1,095.24	$1,095.20	$1,095.30