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	$158.85	7.660%	$171.0179	$171.02	$171.00	$171.00
Purchase #2	$108.33	13.444%	$122.8939	$122.89	$122.90	$122.90
Purchase #3	$193.37	13.104%	$218.7092	$218.71	$218.70	$218.70
Purchase #4	$73.54	12.683%	$82.8671	$82.87	$82.85	$82.90
Purchase #5	$200.38	9.653%	$219.7227	$219.72	$219.70	$219.70
Purchase #6	$90.76	9.119%	$99.0364	$99.04	$99.05	$99.00
Purchase #7	$46.67	7.221%	$50.04	$50.04	$50.05	$50.00
7 purchase totals =	$871.90		$964.2872	$964.29	$964.25	$964.20