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	$39.37	4.304%	$41.0645	$41.06	$41.05	$41.10
Purchase #2	$41.83	5.738%	$44.2302	$44.23	$44.25	$44.20
Purchase #3	$164.66	10.681%	$182.2473	$182.25	$182.25	$182.20
Purchase #4	$35.94	12.598%	$40.4677	$40.47	$40.45	$40.50
Purchase #5	$94.73	5.650%	$100.0822	$100.08	$100.10	$100.10
Purchase #6	$35.56	4.278%	$37.0813	$37.08	$37.10	$37.10
Purchase #7	$224.57	11.872%	$251.231	$251.23	$251.25	$251.20
7 purchase totals =	$636.66		$696.4042	$696.40	$696.45	$696.40