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	$89.27	5.215%	$93.9254	$93.93	$93.95	$93.90
Purchase #2	$122.97	13.793%	$139.9313	$139.93	$139.95	$139.90
Purchase #3	$242.90	13.155%	$274.8535	$274.85	$274.85	$274.90
Purchase #4	$33.76	11.323%	$37.5826	$37.58	$37.60	$37.60
Purchase #5	$210.80	13.239%	$238.7078	$238.71	$238.70	$238.70
Purchase #6	$241.59	8.842%	$262.9514	$262.95	$262.95	$263.00
Purchase #7	$124.83	12.643%	$140.6123	$140.61	$140.60	$140.60
7 purchase totals =	$1,066.12		$1,188.5643	$1,188.56	$1,188.60	$1,188.60