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	$31.37	12.355%	$35.2458	$35.25	$35.25	$35.20
Purchase #2	$75.59	3.851%	$78.501	$78.50	$78.50	$78.50
Purchase #3	$187.34	3.754%	$194.3727	$194.37	$194.35	$194.40
Purchase #4	$177.57	7.432%	$190.767	$190.77	$190.75	$190.80
Purchase #5	$134.70	9.231%	$147.1342	$147.13	$147.15	$147.10
Purchase #6	$111.65	10.871%	$123.7875	$123.79	$123.80	$123.80
Purchase #7	$28.47	3.257%	$29.3973	$29.40	$29.40	$29.40
7 purchase totals =	$746.69		$799.2055	$799.21	$799.20	$799.20