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	$22.78	5.657%	$24.0687	$24.07	$24.05	$24.10
Purchase #2	$245.89	6.665%	$262.2786	$262.28	$262.30	$262.30
Purchase #3	$141.90	12.689%	$159.9057	$159.91	$159.90	$159.90
Purchase #4	$40.81	5.103%	$42.8925	$42.89	$42.90	$42.90
Purchase #5	$199.60	12.589%	$224.7276	$224.73	$224.75	$224.70
Purchase #6	$125.64	9.179%	$137.1725	$137.17	$137.15	$137.20
Purchase #7	$193.75	9.337%	$211.8404	$211.84	$211.85	$211.80
7 purchase totals =	$970.37		$1,062.8860	$1,062.89	$1,062.90	$1,062.90