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	$145.91	10.407%	$161.0949	$161.09	$161.10	$161.10
Purchase #2	$150.46	5.799%	$159.1852	$159.19	$159.20	$159.20
Purchase #3	$152.95	11.696%	$170.839	$170.84	$170.85	$170.80
Purchase #4	$104.56	6.732%	$111.599	$111.60	$111.60	$111.60
Purchase #5	$217.25	3.624%	$225.1231	$225.12	$225.10	$225.10
Purchase #6	$197.96	13.705%	$225.0904	$225.09	$225.10	$225.10
Purchase #7	$233.42	9.399%	$255.3591	$255.36	$255.35	$255.40
7 purchase totals =	$1,202.51		$1,308.2907	$1,308.29	$1,308.30	$1,308.30