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	$116.89	12.476%	$131.4732	$131.47	$131.45	$131.50
Purchase #2	$88.90	13.323%	$100.7441	$100.74	$100.75	$100.70
Purchase #3	$97.99	10.468%	$108.2476	$108.25	$108.25	$108.20
Purchase #4	$168.89	7.155%	$180.9741	$180.97	$180.95	$181.00
Purchase #5	$83.64	6.534%	$89.105	$89.11	$89.10	$89.10
Purchase #6	$243.61	4.500%	$254.5725	$254.57	$254.55	$254.60
Purchase #7	$183.34	6.567%	$195.3799	$195.38	$195.40	$195.40
7 purchase totals =	$983.26		$1,060.4964	$1,060.49	$1,060.45	$1,060.50