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	$142.49	3.137%	$146.9599	$146.96	$146.95	$147.00
Purchase #2	$18.57	12.225%	$20.8402	$20.84	$20.85	$20.80
Purchase #3	$56.86	3.778%	$59.0082	$59.01	$59.00	$59.00
Purchase #4	$198.81	5.434%	$209.6133	$209.61	$209.60	$209.60
Purchase #5	$156.28	9.145%	$170.5718	$170.57	$170.55	$170.60
Purchase #6	$91.88	9.738%	$100.8273	$100.83	$100.85	$100.80
Purchase #7	$235.83	9.500%	$258.2339	$258.23	$258.25	$258.20
7 purchase totals =	$900.72		$966.0546	$966.05	$966.05	$966.00