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	$209.47	7.138%	$224.422	$224.42	$224.40	$224.40
Purchase #2	$125.41	12.240%	$140.7602	$140.76	$140.75	$140.80
Purchase #3	$250.64	4.309%	$261.4401	$261.44	$261.45	$261.40
Purchase #4	$132.38	9.154%	$144.4981	$144.50	$144.50	$144.50
Purchase #5	$34.77	5.456%	$36.6671	$36.67	$36.65	$36.70
Purchase #6	$247.35	3.274%	$255.4482	$255.45	$255.45	$255.40
Purchase #7	$56.71	4.594%	$59.3153	$59.32	$59.30	$59.30
7 purchase totals =	$1,056.73		$1,122.5510	$1,122.56	$1,122.50	$1,122.50