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	$12.57	7.495%	$13.5121	$13.51	$13.50	$13.50
Purchase #2	$29.34	8.573%	$31.8553	$31.86	$31.85	$31.90
Purchase #3	$55.83	8.296%	$60.4617	$60.46	$60.45	$60.50
Purchase #4	$206.25	3.446%	$213.3574	$213.36	$213.35	$213.40
Purchase #5	$71.87	13.216%	$81.3683	$81.37	$81.35	$81.40
Purchase #6	$243.39	7.351%	$261.2816	$261.28	$261.30	$261.30
Purchase #7	$71.94	9.641%	$78.8757	$78.88	$78.90	$78.90
7 purchase totals =	$691.19		$740.7121	$740.72	$740.70	$740.90