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	$162.40	3.833%	$168.6248	$168.62	$168.60	$168.60
Purchase #2	$196.25	13.695%	$223.1264	$223.13	$223.15	$223.10
Purchase #3	$93.51	3.429%	$96.7165	$96.72	$96.70	$96.70
Purchase #4	$202.37	7.747%	$218.0476	$218.05	$218.05	$218.00
Purchase #5	$225.81	4.625%	$236.2537	$236.25	$236.25	$236.30
Purchase #6	$73.92	6.741%	$78.9029	$78.90	$78.90	$78.90
Purchase #7	$37.57	6.339%	$39.9516	$39.95	$39.95	$40.00
7 purchase totals =	$991.83		$1,061.6235	$1,061.62	$1,061.60	$1,061.60