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	$197.38	13.722%	$224.4645	$224.46	$224.45	$224.50
Purchase #2	$103.68	8.820%	$112.8246	$112.82	$112.80	$112.80
Purchase #3	$199.65	6.413%	$212.4536	$212.45	$212.45	$212.50
Purchase #4	$150.42	11.541%	$167.78	$167.78	$167.80	$167.80
Purchase #5	$146.46	3.759%	$151.9654	$151.97	$151.95	$152.00
Purchase #6	$95.90	11.422%	$106.8537	$106.85	$106.85	$106.90
Purchase #7	$71.41	8.797%	$77.6919	$77.69	$77.70	$77.70
7 purchase totals =	$964.90		$1,054.0337	$1,054.02	$1,054.00	$1,054.20