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	$205.66	9.502%	$225.2018	$225.20	$225.20	$225.20
Purchase #2	$47.30	4.480%	$49.419	$49.42	$49.40	$49.40
Purchase #3	$40.96	5.267%	$43.1174	$43.12	$43.10	$43.10
Purchase #4	$234.69	6.826%	$250.7099	$250.71	$250.70	$250.70
Purchase #5	$124.37	13.280%	$140.8863	$140.89	$140.90	$140.90
Purchase #6	$142.91	8.118%	$154.5114	$154.51	$154.50	$154.50
Purchase #7	$208.57	4.394%	$217.7346	$217.73	$217.75	$217.70
7 purchase totals =	$1,004.46		$1,081.5804	$1,081.58	$1,081.55	$1,081.50