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	$153.42	7.139%	$164.3727	$164.37	$164.35	$164.40
Purchase #2	$64.61	10.103%	$71.1375	$71.14	$71.15	$71.10
Purchase #3	$15.55	3.306%	$16.0641	$16.06	$16.05	$16.10
Purchase #4	$39.61	9.741%	$43.4684	$43.47	$43.45	$43.50
Purchase #5	$235.81	11.762%	$263.546	$263.55	$263.55	$263.50
Purchase #6	$85.86	7.193%	$92.0359	$92.04	$92.05	$92.00
Purchase #7	$162.69	13.364%	$184.4319	$184.43	$184.45	$184.40
7 purchase totals =	$757.55		$835.0565	$835.06	$835.05	$835.00