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	$155.77	8.456%	$168.9419	$168.94	$168.95	$168.90
Purchase #2	$95.43	10.835%	$105.7698	$105.77	$105.75	$105.80
Purchase #3	$115.59	7.781%	$124.5841	$124.58	$124.60	$124.60
Purchase #4	$68.99	5.433%	$72.7382	$72.74	$72.75	$72.70
Purchase #5	$195.85	10.142%	$215.7131	$215.71	$215.70	$215.70
Purchase #6	$169.32	5.541%	$178.702	$178.70	$178.70	$178.70
Purchase #7	$63.99	11.742%	$71.5037	$71.50	$71.50	$71.50
7 purchase totals =	$864.94		$937.9528	$937.94	$937.95	$937.90