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	$42.57	3.195%	$43.9301	$43.93	$43.95	$43.90
Purchase #2	$250.43	4.192%	$260.928	$260.93	$260.95	$260.90
Purchase #3	$96.27	4.381%	$100.4876	$100.49	$100.50	$100.50
Purchase #4	$188.98	5.733%	$199.8142	$199.81	$199.80	$199.80
Purchase #5	$84.44	9.563%	$92.515	$92.52	$92.50	$92.50
Purchase #6	$39.96	13.270%	$45.2627	$45.26	$45.25	$45.30
Purchase #7	$155.96	6.575%	$166.2144	$166.21	$166.20	$166.20
7 purchase totals =	$858.61		$909.1520	$909.15	$909.15	$909.10