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	$43.61	3.329%	$45.0618	$45.06	$45.05	$45.10
Purchase #2	$165.63	11.180%	$184.1474	$184.15	$184.15	$184.10
Purchase #3	$140.63	7.606%	$151.3263	$151.33	$151.35	$151.30
Purchase #4	$54.58	9.706%	$59.8775	$59.88	$59.90	$59.90
Purchase #5	$173.73	6.224%	$184.543	$184.54	$184.55	$184.50
Purchase #6	$64.78	6.431%	$68.946	$68.95	$68.95	$68.90
Purchase #7	$123.43	13.849%	$140.5238	$140.52	$140.50	$140.50
7 purchase totals =	$766.39		$834.4258	$834.43	$834.45	$834.30