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	$137.31	11.403%	$152.9675	$152.97	$152.95	$153.00
Purchase #2	$87.28	9.492%	$95.5646	$95.56	$95.55	$95.60
Purchase #3	$107.38	4.178%	$111.8663	$111.87	$111.85	$111.90
Purchase #4	$107.85	10.799%	$119.4967	$119.50	$119.50	$119.50
Purchase #5	$223.57	6.185%	$237.3978	$237.40	$237.40	$237.40
Purchase #6	$52.47	10.377%	$57.9148	$57.91	$57.90	$57.90
Purchase #7	$247.59	8.109%	$267.6671	$267.67	$267.65	$267.70
7 purchase totals =	$963.45		$1,042.8748	$1,042.88	$1,042.80	$1,043.00