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	$237.64	10.395%	$262.3427	$262.34	$262.35	$262.30
Purchase #2	$142.33	7.468%	$152.9592	$152.96	$152.95	$153.00
Purchase #3	$146.58	8.853%	$159.5567	$159.56	$159.55	$159.60
Purchase #4	$225.73	6.665%	$240.7749	$240.77	$240.75	$240.80
Purchase #5	$175.49	9.314%	$191.8351	$191.84	$191.85	$191.80
Purchase #6	$177.57	4.738%	$185.9833	$185.98	$186.00	$186.00
Purchase #7	$54.56	13.721%	$62.0462	$62.05	$62.05	$62.00
7 purchase totals =	$1,159.90		$1,255.4981	$1,255.50	$1,255.50	$1,255.50