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	$163.38	5.404%	$172.2091	$172.21	$172.20	$172.20
Purchase #2	$41.83	5.398%	$44.088	$44.09	$44.10	$44.10
Purchase #3	$36.83	9.477%	$40.3204	$40.32	$40.30	$40.30
Purchase #4	$188.31	6.168%	$199.925	$199.93	$199.95	$199.90
Purchase #5	$143.98	7.369%	$154.5899	$154.59	$154.60	$154.60
Purchase #6	$165.40	6.685%	$176.457	$176.46	$176.45	$176.50
Purchase #7	$249.67	10.475%	$275.8229	$275.82	$275.80	$275.80
7 purchase totals =	$989.40		$1,063.4123	$1,063.42	$1,063.40	$1,063.40