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	$190.54	5.226%	$200.4976	$200.50	$200.50	$200.50
Purchase #2	$35.28	6.448%	$37.5549	$37.55	$37.55	$37.60
Purchase #3	$138.39	9.571%	$151.6353	$151.64	$151.65	$151.60
Purchase #4	$153.36	6.610%	$163.4971	$163.50	$163.50	$163.50
Purchase #5	$181.34	8.145%	$196.1101	$196.11	$196.10	$196.10
Purchase #6	$58.62	10.405%	$64.7194	$64.72	$64.70	$64.70
Purchase #7	$131.96	4.237%	$137.5511	$137.55	$137.55	$137.60
7 purchase totals =	$889.49		$951.5655	$951.57	$951.55	$951.60