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	$100.89	3.288%	$104.2073	$104.21	$104.20	$104.20
Purchase #2	$140.37	7.677%	$151.1462	$151.15	$151.15	$151.10
Purchase #3	$118.62	11.219%	$131.928	$131.93	$131.95	$131.90
Purchase #4	$223.38	6.772%	$238.5073	$238.51	$238.50	$238.50
Purchase #5	$220.90	5.385%	$232.7955	$232.80	$232.80	$232.80
Purchase #6	$130.90	8.618%	$142.181	$142.18	$142.20	$142.20
Purchase #7	$231.43	13.469%	$262.6013	$262.60	$262.60	$262.60
7 purchase totals =	$1,166.49		$1,263.3666	$1,263.38	$1,263.40	$1,263.30