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	$199.70	4.388%	$208.4628	$208.46	$208.45	$208.50
Purchase #2	$164.95	8.682%	$179.271	$179.27	$179.25	$179.30
Purchase #3	$96.37	13.322%	$109.2084	$109.21	$109.20	$109.20
Purchase #4	$166.28	5.598%	$175.5884	$175.59	$175.60	$175.60
Purchase #5	$31.53	6.496%	$33.5782	$33.58	$33.60	$33.60
Purchase #6	$109.58	8.203%	$118.5688	$118.57	$118.55	$118.60
Purchase #7	$139.95	8.147%	$151.3517	$151.35	$151.35	$151.40
7 purchase totals =	$908.36		$976.0293	$976.03	$976.00	$976.20