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	$63.31	13.388%	$71.7859	$71.79	$71.80	$71.80
Purchase #2	$140.77	10.721%	$155.862	$155.86	$155.85	$155.90
Purchase #3	$220.55	6.866%	$235.693	$235.69	$235.70	$235.70
Purchase #4	$19.66	10.168%	$21.659	$21.66	$21.65	$21.70
Purchase #5	$233.48	10.693%	$258.446	$258.45	$258.45	$258.40
Purchase #6	$140.68	6.727%	$150.1435	$150.14	$150.15	$150.10
Purchase #7	$123.29	6.489%	$131.2903	$131.29	$131.30	$131.30
7 purchase totals =	$941.74		$1,024.8797	$1,024.88	$1,024.90	$1,024.90