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	$37.29	9.158%	$40.705	$40.71	$40.70	$40.70
Purchase #2	$100.33	4.239%	$104.583	$104.58	$104.60	$104.60
Purchase #3	$45.65	3.499%	$47.2473	$47.25	$47.25	$47.20
Purchase #4	$109.93	13.220%	$124.4627	$124.46	$124.45	$124.50
Purchase #5	$239.35	9.439%	$261.9422	$261.94	$261.95	$261.90
Purchase #6	$82.80	11.130%	$92.0156	$92.02	$92.00	$92.00
Purchase #7	$205.85	11.395%	$229.3066	$229.31	$229.30	$229.30
7 purchase totals =	$821.20		$900.2624	$900.27	$900.25	$900.20