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	$125.32	12.851%	$141.4249	$141.42	$141.40	$141.40
Purchase #2	$182.68	7.531%	$196.4376	$196.44	$196.45	$196.40
Purchase #3	$33.73	7.657%	$36.3127	$36.31	$36.30	$36.30
Purchase #4	$67.48	7.303%	$72.4081	$72.41	$72.40	$72.40
Purchase #5	$19.37	9.108%	$21.1342	$21.13	$21.15	$21.10
Purchase #6	$205.88	3.784%	$213.6705	$213.67	$213.65	$213.70
Purchase #7	$104.95	11.518%	$117.0381	$117.04	$117.05	$117.00
7 purchase totals =	$739.41		$798.4261	$798.42	$798.40	$798.30