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	$181.49	10.607%	$200.7406	$200.74	$200.75	$200.70
Purchase #2	$123.89	13.421%	$140.5173	$140.52	$140.50	$140.50
Purchase #3	$66.31	8.111%	$71.6884	$71.69	$71.70	$71.70
Purchase #4	$212.84	12.306%	$239.0321	$239.03	$239.05	$239.00
Purchase #5	$196.33	10.550%	$217.0428	$217.04	$217.05	$217.00
Purchase #6	$112.63	3.723%	$116.8232	$116.82	$116.80	$116.80
Purchase #7	$6.41	10.777%	$7.1008	$7.10	$7.10	$7.10
7 purchase totals =	$899.90		$992.9452	$992.94	$992.95	$992.80