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	$82.37	10.697%	$91.1811	$91.18	$91.20	$91.20
Purchase #2	$69.94	11.724%	$78.1398	$78.14	$78.15	$78.10
Purchase #3	$52.93	11.694%	$59.1196	$59.12	$59.10	$59.10
Purchase #4	$225.48	8.572%	$244.8081	$244.81	$244.80	$244.80
Purchase #5	$203.81	11.630%	$227.5131	$227.51	$227.50	$227.50
Purchase #6	$74.71	3.477%	$77.3077	$77.31	$77.30	$77.30
Purchase #7	$229.67	3.847%	$238.5054	$238.51	$238.50	$238.50
7 purchase totals =	$938.91		$1,016.5748	$1,016.58	$1,016.55	$1,016.50