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	$204.26	9.315%	$223.2868	$223.29	$223.30	$223.30
Purchase #2	$87.66	3.403%	$90.6431	$90.64	$90.65	$90.60
Purchase #3	$214.39	9.747%	$235.2866	$235.29	$235.30	$235.30
Purchase #4	$94.81	8.506%	$102.8745	$102.87	$102.85	$102.90
Purchase #5	$37.91	5.171%	$39.8703	$39.87	$39.85	$39.90
Purchase #6	$148.72	9.507%	$162.8588	$162.86	$162.85	$162.90
Purchase #7	$45.86	12.656%	$51.664	$51.66	$51.65	$51.70
7 purchase totals =	$833.61		$906.4841	$906.48	$906.45	$906.60