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	$86.72	7.412%	$93.1477	$93.15	$93.15	$93.10
Purchase #2	$235.79	10.329%	$260.1447	$260.14	$260.15	$260.10
Purchase #3	$183.90	6.599%	$196.0356	$196.04	$196.05	$196.00
Purchase #4	$203.68	9.211%	$222.441	$222.44	$222.45	$222.40
Purchase #5	$82.66	9.437%	$90.4606	$90.46	$90.45	$90.50
Purchase #6	$160.97	6.533%	$171.4862	$171.49	$171.50	$171.50
Purchase #7	$212.45	13.767%	$241.698	$241.70	$241.70	$241.70
7 purchase totals =	$1,166.17		$1,275.4138	$1,275.42	$1,275.45	$1,275.30