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	$175.77	7.250%	$188.5133	$188.51	$188.50	$188.50
Purchase #2	$240.98	6.522%	$256.6967	$256.70	$256.70	$256.70
Purchase #3	$186.54	5.550%	$196.893	$196.89	$196.90	$196.90
Purchase #4	$30.39	11.601%	$33.9155	$33.92	$33.90	$33.90
Purchase #5	$68.81	8.249%	$74.4861	$74.49	$74.50	$74.50
Purchase #6	$92.88	10.609%	$102.7336	$102.73	$102.75	$102.70
Purchase #7	$20.88	6.557%	$22.2491	$22.25	$22.25	$22.20
7 purchase totals =	$816.25		$875.4873	$875.49	$875.50	$875.40