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	$134.43	4.689%	$140.7334	$140.73	$140.75	$140.70
Purchase #2	$86.57	10.435%	$95.6036	$95.60	$95.60	$95.60
Purchase #3	$75.72	13.311%	$85.7991	$85.80	$85.80	$85.80
Purchase #4	$158.54	12.356%	$178.1292	$178.13	$178.15	$178.10
Purchase #5	$151.72	3.238%	$156.6327	$156.63	$156.65	$156.60
Purchase #6	$54.79	8.659%	$59.5343	$59.53	$59.55	$59.50
Purchase #7	$40.47	12.573%	$45.5583	$45.56	$45.55	$45.60
7 purchase totals =	$702.24		$761.9906	$761.98	$762.05	$761.90