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	$94.25	10.424%	$104.0746	$104.07	$104.05	$104.10
Purchase #2	$67.47	8.117%	$72.9465	$72.95	$72.95	$72.90
Purchase #3	$145.36	10.464%	$160.5705	$160.57	$160.55	$160.60
Purchase #4	$211.80	9.355%	$231.6139	$231.61	$231.60	$231.60
Purchase #5	$161.85	10.668%	$179.1162	$179.12	$179.10	$179.10
Purchase #6	$203.29	13.521%	$230.7768	$230.78	$230.80	$230.80
Purchase #7	$59.58	11.760%	$66.5866	$66.59	$66.60	$66.60
7 purchase totals =	$943.60		$1,045.6851	$1,045.69	$1,045.65	$1,045.70