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	$104.98	9.178%	$114.6151	$114.62	$114.60	$114.60
Purchase #2	$63.92	11.612%	$71.3424	$71.34	$71.35	$71.30
Purchase #3	$94.53	11.793%	$105.6779	$105.68	$105.70	$105.70
Purchase #4	$219.73	8.454%	$238.306	$238.31	$238.30	$238.30
Purchase #5	$192.36	13.300%	$217.9439	$217.94	$217.95	$217.90
Purchase #6	$56.32	10.143%	$62.0325	$62.03	$62.05	$62.00
Purchase #7	$80.46	10.503%	$88.9107	$88.91	$88.90	$88.90
7 purchase totals =	$812.30		$898.8285	$898.83	$898.85	$898.70