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	$74.34	10.322%	$82.0134	$82.01	$82.00	$82.00
Purchase #2	$238.35	5.651%	$251.8192	$251.82	$251.80	$251.80
Purchase #3	$95.32	13.415%	$108.1072	$108.11	$108.10	$108.10
Purchase #4	$71.94	5.343%	$75.7838	$75.78	$75.80	$75.80
Purchase #5	$243.54	13.157%	$275.5826	$275.58	$275.60	$275.60
Purchase #6	$189.85	12.146%	$212.9092	$212.91	$212.90	$212.90
Purchase #7	$56.91	9.795%	$62.4843	$62.48	$62.50	$62.50
7 purchase totals =	$970.25		$1,068.6997	$1,068.69	$1,068.70	$1,068.70