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	$86.97	3.144%	$89.7043	$89.70	$89.70	$89.70
Purchase #2	$46.26	5.835%	$48.9593	$48.96	$48.95	$49.00
Purchase #3	$115.39	13.423%	$130.8788	$130.88	$130.90	$130.90
Purchase #4	$96.65	4.359%	$100.863	$100.86	$100.85	$100.90
Purchase #5	$160.25	7.690%	$172.5732	$172.57	$172.55	$172.60
Purchase #6	$147.37	5.699%	$155.7686	$155.77	$155.75	$155.80
Purchase #7	$69.82	8.211%	$75.5529	$75.55	$75.55	$75.60
7 purchase totals =	$722.71		$774.3001	$774.29	$774.25	$774.50