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	$172.85	10.404%	$190.8333	$190.83	$190.85	$190.80
Purchase #2	$100.63	10.747%	$111.4447	$111.44	$111.45	$111.40
Purchase #3	$137.48	9.759%	$150.8967	$150.90	$150.90	$150.90
Purchase #4	$158.72	3.726%	$164.6339	$164.63	$164.65	$164.60
Purchase #5	$247.55	9.365%	$270.7331	$270.73	$270.75	$270.70
Purchase #6	$176.37	8.682%	$191.6824	$191.68	$191.70	$191.70
Purchase #7	$210.37	10.794%	$233.0773	$233.08	$233.10	$233.10
7 purchase totals =	$1,203.97		$1,313.3014	$1,313.29	$1,313.40	$1,313.20