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	$247.35	9.854%	$271.7239	$271.72	$271.70	$271.70
Purchase #2	$235.27	12.314%	$264.2411	$264.24	$264.25	$264.20
Purchase #3	$111.89	3.760%	$116.0971	$116.10	$116.10	$116.10
Purchase #4	$138.63	3.594%	$143.6124	$143.61	$143.60	$143.60
Purchase #5	$23.69	4.147%	$24.6724	$24.67	$24.65	$24.70
Purchase #6	$40.37	6.807%	$43.118	$43.12	$43.10	$43.10
Purchase #7	$134.66	10.619%	$148.9595	$148.96	$148.95	$149.00
7 purchase totals =	$931.86		$1,012.4244	$1,012.42	$1,012.35	$1,012.40