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	$124.82	13.669%	$141.8816	$141.88	$141.90	$141.90
Purchase #2	$137.66	3.133%	$141.9729	$141.97	$141.95	$142.00
Purchase #3	$98.95	4.570%	$103.472	$103.47	$103.45	$103.50
Purchase #4	$49.37	13.309%	$55.9407	$55.94	$55.95	$55.90
Purchase #5	$140.72	7.283%	$150.9686	$150.97	$150.95	$151.00
Purchase #6	$151.80	6.848%	$162.1953	$162.20	$162.20	$162.20
Purchase #7	$156.53	10.170%	$172.4491	$172.45	$172.45	$172.40
7 purchase totals =	$859.85		$928.8802	$928.88	$928.85	$928.90