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	$214.34	9.103%	$233.8514	$233.85	$233.85	$233.90
Purchase #2	$66.27	3.284%	$68.4463	$68.45	$68.45	$68.40
Purchase #3	$173.40	9.731%	$190.2736	$190.27	$190.25	$190.30
Purchase #4	$40.59	9.459%	$44.4294	$44.43	$44.45	$44.40
Purchase #5	$103.48	12.674%	$116.5951	$116.60	$116.60	$116.60
Purchase #6	$43.74	7.756%	$47.1325	$47.13	$47.15	$47.10
Purchase #7	$129.57	3.523%	$134.1348	$134.13	$134.15	$134.10
7 purchase totals =	$771.39		$834.8631	$834.86	$834.90	$834.80