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	$169.94	9.322%	$185.7818	$185.78	$185.80	$185.80
Purchase #2	$38.65	5.581%	$40.8071	$40.81	$40.80	$40.80
Purchase #3	$37.30	8.179%	$40.3508	$40.35	$40.35	$40.40
Purchase #4	$107.43	4.858%	$112.6489	$112.65	$112.65	$112.60
Purchase #5	$141.41	7.694%	$152.2901	$152.29	$152.30	$152.30
Purchase #6	$199.29	10.178%	$219.5737	$219.57	$219.55	$219.60
Purchase #7	$159.38	10.122%	$175.5124	$175.51	$175.50	$175.50
7 purchase totals =	$853.40		$926.9648	$926.96	$926.95	$927.00