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	$114.94	7.801%	$123.9065	$123.91	$123.90	$123.90
Purchase #2	$134.50	13.447%	$152.5862	$152.59	$152.60	$152.60
Purchase #3	$32.94	13.365%	$37.3424	$37.34	$37.35	$37.30
Purchase #4	$202.50	6.394%	$215.4479	$215.45	$215.45	$215.40
Purchase #5	$7.95	13.566%	$9.0285	$9.03	$9.05	$9.00
Purchase #6	$234.84	4.520%	$245.4548	$245.45	$245.45	$245.50
Purchase #7	$68.87	13.652%	$78.2721	$78.27	$78.25	$78.30
7 purchase totals =	$796.54		$862.0384	$862.04	$862.05	$862.00