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	$89.87	8.292%	$97.322	$97.32	$97.30	$97.30
Purchase #2	$11.28	4.102%	$11.7427	$11.74	$11.75	$11.70
Purchase #3	$40.78	5.152%	$42.881	$42.88	$42.90	$42.90
Purchase #4	$231.85	12.242%	$260.2331	$260.23	$260.25	$260.20
Purchase #5	$124.70	12.740%	$140.5868	$140.59	$140.60	$140.60
Purchase #6	$221.75	3.537%	$229.5933	$229.59	$229.60	$229.60
Purchase #7	$35.30	12.117%	$39.5773	$39.58	$39.60	$39.60
7 purchase totals =	$755.53		$821.9362	$821.93	$822.00	$821.90