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	$213.54	5.509%	$225.3039	$225.30	$225.30	$225.30
Purchase #2	$218.26	5.696%	$230.6921	$230.69	$230.70	$230.70
Purchase #3	$109.41	11.105%	$121.56	$121.56	$121.55	$121.60
Purchase #4	$169.30	9.339%	$185.1109	$185.11	$185.10	$185.10
Purchase #5	$235.46	8.186%	$254.7348	$254.73	$254.75	$254.70
Purchase #6	$120.91	6.109%	$128.2964	$128.30	$128.30	$128.30
Purchase #7	$50.51	8.468%	$54.7872	$54.79	$54.80	$54.80
7 purchase totals =	$1,117.39		$1,200.4853	$1,200.48	$1,200.50	$1,200.50