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	$214.90	8.777%	$233.7618	$233.76	$233.75	$233.80
Purchase #2	$62.50	8.109%	$67.5681	$67.57	$67.55	$67.60
Purchase #3	$41.79	3.315%	$43.1753	$43.18	$43.20	$43.20
Purchase #4	$84.72	6.386%	$90.1302	$90.13	$90.15	$90.10
Purchase #5	$175.46	8.426%	$190.2443	$190.24	$190.25	$190.20
Purchase #6	$240.49	11.299%	$267.663	$267.66	$267.65	$267.70
Purchase #7	$187.68	6.603%	$200.0725	$200.07	$200.05	$200.10
7 purchase totals =	$1,007.54		$1,092.6152	$1,092.61	$1,092.60	$1,092.70