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	$238.79	4.867%	$250.4119	$250.41	$250.40	$250.40
Purchase #2	$40.75	11.695%	$45.5157	$45.52	$45.50	$45.50
Purchase #3	$112.89	7.633%	$121.5069	$121.51	$121.50	$121.50
Purchase #4	$192.33	12.431%	$216.2385	$216.24	$216.25	$216.20
Purchase #5	$220.55	11.209%	$245.2714	$245.27	$245.25	$245.30
Purchase #6	$213.72	5.546%	$225.5729	$225.57	$225.55	$225.60
Purchase #7	$105.82	13.357%	$119.9544	$119.95	$119.95	$120.00
7 purchase totals =	$1,124.85		$1,224.4717	$1,224.47	$1,224.40	$1,224.50