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	$158.39	8.163%	$171.3194	$171.32	$171.30	$171.30
Purchase #2	$200.85	9.559%	$220.0493	$220.05	$220.05	$220.00
Purchase #3	$220.42	12.436%	$247.8314	$247.83	$247.85	$247.80
Purchase #4	$114.79	7.829%	$123.7769	$123.78	$123.80	$123.80
Purchase #5	$83.32	6.156%	$88.4492	$88.45	$88.45	$88.40
Purchase #6	$33.98	8.490%	$36.8649	$36.86	$36.85	$36.90
Purchase #7	$112.53	4.483%	$117.5747	$117.57	$117.55	$117.60
7 purchase totals =	$924.28		$1,005.8658	$1,005.86	$1,005.85	$1,005.80