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	$220.53	7.182%	$236.3685	$236.37	$236.35	$236.40
Purchase #2	$247.68	11.790%	$276.8815	$276.88	$276.90	$276.90
Purchase #3	$222.52	8.451%	$241.3252	$241.33	$241.35	$241.30
Purchase #4	$82.76	6.651%	$88.2644	$88.26	$88.25	$88.30
Purchase #5	$34.27	3.262%	$35.3879	$35.39	$35.40	$35.40
Purchase #6	$87.31	13.859%	$99.4103	$99.41	$99.40	$99.40
Purchase #7	$77.34	7.265%	$82.9588	$82.96	$82.95	$83.00
7 purchase totals =	$972.41		$1,060.5966	$1,060.60	$1,060.60	$1,060.70