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	$162.63	6.290%	$172.8594	$172.86	$172.85	$172.90
Purchase #2	$142.72	10.620%	$157.8769	$157.88	$157.90	$157.90
Purchase #3	$220.63	12.380%	$247.944	$247.94	$247.95	$247.90
Purchase #4	$131.29	11.289%	$146.1113	$146.11	$146.10	$146.10
Purchase #5	$250.66	9.339%	$274.0691	$274.07	$274.05	$274.10
Purchase #6	$165.32	4.216%	$172.2899	$172.29	$172.30	$172.30
Purchase #7	$97.59	7.693%	$105.0976	$105.10	$105.10	$105.10
7 purchase totals =	$1,170.84		$1,276.2482	$1,276.25	$1,276.25	$1,276.30