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	$193.31	13.268%	$218.9584	$218.96	$218.95	$219.00
Purchase #2	$132.55	13.863%	$150.9254	$150.93	$150.95	$150.90
Purchase #3	$40.69	3.596%	$42.1532	$42.15	$42.15	$42.20
Purchase #4	$97.87	3.702%	$101.4931	$101.49	$101.50	$101.50
Purchase #5	$222.67	9.293%	$243.3627	$243.36	$243.35	$243.40
Purchase #6	$220.62	10.244%	$243.2203	$243.22	$243.20	$243.20
Purchase #7	$157.60	6.767%	$168.2648	$168.26	$168.25	$168.30
7 purchase totals =	$1,065.31		$1,168.3779	$1,168.37	$1,168.35	$1,168.50