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	$192.83	13.258%	$218.3954	$218.40	$218.40	$218.40
Purchase #2	$58.86	11.105%	$65.3964	$65.40	$65.40	$65.40
Purchase #3	$39.50	7.641%	$42.5182	$42.52	$42.50	$42.50
Purchase #4	$110.25	5.648%	$116.4769	$116.48	$116.50	$116.50
Purchase #5	$81.46	8.249%	$88.1796	$88.18	$88.20	$88.20
Purchase #6	$50.75	8.130%	$54.876	$54.88	$54.90	$54.90
Purchase #7	$151.53	11.705%	$169.2666	$169.27	$169.25	$169.30
7 purchase totals =	$685.18		$755.1091	$755.13	$755.15	$755.20