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	$59.66	5.329%	$62.8393	$62.84	$62.85	$62.80
Purchase #2	$204.36	9.839%	$224.467	$224.47	$224.45	$224.50
Purchase #3	$213.82	10.587%	$236.4571	$236.46	$236.45	$236.50
Purchase #4	$243.78	4.699%	$255.2352	$255.24	$255.25	$255.20
Purchase #5	$92.56	8.326%	$100.2665	$100.27	$100.25	$100.30
Purchase #6	$235.97	3.501%	$244.2313	$244.23	$244.25	$244.20
Purchase #7	$7.60	13.479%	$8.6244	$8.62	$8.60	$8.60
7 purchase totals =	$1,057.75		$1,132.1208	$1,132.13	$1,132.10	$1,132.10