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	$64.73	7.443%	$69.5479	$69.55	$69.55	$69.50
Purchase #2	$185.93	12.759%	$209.6528	$209.65	$209.65	$209.70
Purchase #3	$147.99	8.275%	$160.2362	$160.24	$160.25	$160.20
Purchase #4	$148.51	5.660%	$156.9157	$156.92	$156.90	$156.90
Purchase #5	$146.47	4.329%	$152.8107	$152.81	$152.80	$152.80
Purchase #6	$116.52	6.324%	$123.8887	$123.89	$123.90	$123.90
Purchase #7	$211.91	12.668%	$238.7548	$238.75	$238.75	$238.80
7 purchase totals =	$1,022.06		$1,111.8068	$1,111.81	$1,111.80	$1,111.80