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	$158.72	8.342%	$171.9604	$171.96	$171.95	$172.00
Purchase #2	$238.98	9.254%	$261.0952	$261.10	$261.10	$261.10
Purchase #3	$243.36	4.188%	$253.5519	$253.55	$253.55	$253.60
Purchase #4	$15.67	5.642%	$16.5541	$16.55	$16.55	$16.60
Purchase #5	$140.42	7.870%	$151.4711	$151.47	$151.45	$151.50
Purchase #6	$246.48	7.455%	$264.8551	$264.86	$264.85	$264.90
Purchase #7	$94.56	9.230%	$103.2879	$103.29	$103.30	$103.30
7 purchase totals =	$1,138.19		$1,222.7757	$1,222.78	$1,222.75	$1,223.00