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	$60.91	3.295%	$62.917	$62.92	$62.90	$62.90
Purchase #2	$216.54	6.542%	$230.706	$230.71	$230.70	$230.70
Purchase #3	$243.55	8.725%	$264.7997	$264.80	$264.80	$264.80
Purchase #4	$37.57	10.542%	$41.5306	$41.53	$41.55	$41.50
Purchase #5	$247.42	11.723%	$276.425	$276.43	$276.45	$276.40
Purchase #6	$142.66	5.455%	$150.4421	$150.44	$150.45	$150.40
Purchase #7	$164.68	11.674%	$183.9047	$183.90	$183.90	$183.90
7 purchase totals =	$1,113.33		$1,210.7251	$1,210.73	$1,210.75	$1,210.60