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	$186.62	9.231%	$203.8469	$203.85	$203.85	$203.80
Purchase #2	$126.58	8.334%	$137.1292	$137.13	$137.15	$137.10
Purchase #3	$186.40	5.190%	$196.0742	$196.07	$196.05	$196.10
Purchase #4	$52.62	12.632%	$59.267	$59.27	$59.25	$59.30
Purchase #5	$12.60	5.270%	$13.264	$13.26	$13.25	$13.30
Purchase #6	$169.37	12.465%	$190.482	$190.48	$190.50	$190.50
Purchase #7	$64.43	12.761%	$72.6519	$72.65	$72.65	$72.70
7 purchase totals =	$798.62		$872.7152	$872.71	$872.70	$872.80