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	$218.88	8.794%	$238.1283	$238.13	$238.15	$238.10
Purchase #2	$215.83	10.651%	$238.8181	$238.82	$238.80	$238.80
Purchase #3	$227.53	10.564%	$251.5663	$251.57	$251.55	$251.60
Purchase #4	$7.67	3.521%	$7.9401	$7.94	$7.95	$7.90
Purchase #5	$113.73	7.543%	$122.3087	$122.31	$122.30	$122.30
Purchase #6	$33.31	7.277%	$35.734	$35.73	$35.75	$35.70
Purchase #7	$193.76	11.772%	$216.5694	$216.57	$216.55	$216.60
7 purchase totals =	$1,010.71		$1,111.0649	$1,111.07	$1,111.05	$1,111.00