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	$191.78	10.305%	$211.5429	$211.54	$211.55	$211.50
Purchase #2	$46.53	8.495%	$50.4827	$50.48	$50.50	$50.50
Purchase #3	$132.36	3.633%	$137.1686	$137.17	$137.15	$137.20
Purchase #4	$11.34	7.356%	$12.1742	$12.17	$12.15	$12.20
Purchase #5	$68.93	5.205%	$72.5178	$72.52	$72.50	$72.50
Purchase #6	$188.82	10.365%	$208.3912	$208.39	$208.40	$208.40
Purchase #7	$44.41	5.443%	$46.8272	$46.83	$46.85	$46.80
7 purchase totals =	$684.17		$739.1046	$739.10	$739.10	$739.10