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	$43.95	10.711%	$48.6575	$48.66	$48.65	$48.70
Purchase #2	$87.67	12.266%	$98.4236	$98.42	$98.40	$98.40
Purchase #3	$99.38	13.110%	$112.4087	$112.41	$112.40	$112.40
Purchase #4	$162.62	10.765%	$180.126	$180.13	$180.15	$180.10
Purchase #5	$193.53	10.830%	$214.4893	$214.49	$214.50	$214.50
Purchase #6	$39.53	7.567%	$42.5212	$42.52	$42.50	$42.50
Purchase #7	$74.83	3.590%	$77.5164	$77.52	$77.50	$77.50
7 purchase totals =	$701.51		$774.1427	$774.15	$774.10	$774.10