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	$248.91	4.350%	$259.7376	$259.74	$259.75	$259.70
Purchase #2	$174.54	6.196%	$185.3545	$185.35	$185.35	$185.40
Purchase #3	$66.50	13.129%	$75.2308	$75.23	$75.25	$75.20
Purchase #4	$134.75	13.268%	$152.6286	$152.63	$152.65	$152.60
Purchase #5	$66.57	7.846%	$71.7931	$71.79	$71.80	$71.80
Purchase #6	$36.38	3.566%	$37.6773	$37.68	$37.70	$37.70
Purchase #7	$73.82	6.276%	$78.4529	$78.45	$78.45	$78.50
7 purchase totals =	$801.47		$860.8748	$860.87	$860.95	$860.90