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	$65.97	9.699%	$72.3684	$72.37	$72.35	$72.40
Purchase #2	$96.83	9.857%	$106.3745	$106.37	$106.35	$106.40
Purchase #3	$103.43	4.842%	$108.4381	$108.44	$108.45	$108.40
Purchase #4	$157.63	5.366%	$166.0884	$166.09	$166.10	$166.10
Purchase #5	$124.72	5.359%	$131.4037	$131.40	$131.40	$131.40
Purchase #6	$195.33	10.315%	$215.4783	$215.48	$215.50	$215.50
Purchase #7	$231.44	12.790%	$261.0412	$261.04	$261.05	$261.00
7 purchase totals =	$975.35		$1,061.1926	$1,061.19	$1,061.20	$1,061.20