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	$78.50	6.156%	$83.3325	$83.33	$83.35	$83.30
Purchase #2	$126.79	4.373%	$132.3345	$132.33	$132.35	$132.30
Purchase #3	$142.72	6.199%	$151.5672	$151.57	$151.55	$151.60
Purchase #4	$191.56	8.697%	$208.22	$208.22	$208.20	$208.20
Purchase #5	$147.82	5.642%	$156.16	$156.16	$156.15	$156.20
Purchase #6	$22.63	5.258%	$23.8199	$23.82	$23.80	$23.80
Purchase #7	$228.34	8.534%	$247.8265	$247.83	$247.85	$247.80
7 purchase totals =	$938.36		$1,003.2606	$1,003.26	$1,003.25	$1,003.20