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	$188.89	6.146%	$200.4992	$200.50	$200.50	$200.50
Purchase #2	$183.67	7.179%	$196.8557	$196.86	$196.85	$196.90
Purchase #3	$41.74	7.678%	$44.9448	$44.94	$44.95	$44.90
Purchase #4	$68.53	4.515%	$71.6241	$71.62	$71.60	$71.60
Purchase #5	$244.43	7.513%	$262.794	$262.79	$262.80	$262.80
Purchase #6	$29.91	9.392%	$32.7191	$32.72	$32.70	$32.70
Purchase #7	$118.29	8.341%	$128.1566	$128.16	$128.15	$128.20
7 purchase totals =	$875.46		$937.5935	$937.59	$937.55	$937.60