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	$195.60	10.724%	$216.5761	$216.58	$216.60	$216.60
Purchase #2	$178.32	3.860%	$185.2032	$185.20	$185.20	$185.20
Purchase #3	$66.98	7.577%	$72.0551	$72.06	$72.05	$72.10
Purchase #4	$87.70	5.165%	$92.2297	$92.23	$92.25	$92.20
Purchase #5	$217.34	7.544%	$233.7361	$233.74	$233.75	$233.70
Purchase #6	$84.56	5.483%	$89.1964	$89.20	$89.20	$89.20
Purchase #7	$50.86	3.748%	$52.7662	$52.77	$52.75	$52.80
7 purchase totals =	$881.36		$941.7628	$941.78	$941.80	$941.80