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	$78.32	3.750%	$81.257	$81.26	$81.25	$81.30
Purchase #2	$213.49	11.819%	$238.7224	$238.72	$238.70	$238.70
Purchase #3	$24.95	10.719%	$27.6244	$27.62	$27.60	$27.60
Purchase #4	$221.68	4.260%	$231.1236	$231.12	$231.10	$231.10
Purchase #5	$10.60	4.661%	$11.0941	$11.09	$11.10	$11.10
Purchase #6	$99.34	3.723%	$103.0384	$103.04	$103.05	$103.00
Purchase #7	$67.60	5.397%	$71.2484	$71.25	$71.25	$71.20
7 purchase totals =	$715.98		$764.1083	$764.10	$764.05	$764.00