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	$44.51	9.844%	$48.8916	$48.89	$48.90	$48.90
Purchase #2	$67.48	4.731%	$70.6725	$70.67	$70.65	$70.70
Purchase #3	$109.35	5.851%	$115.7481	$115.75	$115.75	$115.70
Purchase #4	$99.50	9.572%	$109.0241	$109.02	$109.00	$109.00
Purchase #5	$94.52	10.519%	$104.4626	$104.46	$104.45	$104.50
Purchase #6	$86.75	9.285%	$94.8047	$94.80	$94.80	$94.80
Purchase #7	$177.76	6.259%	$188.886	$188.89	$188.90	$188.90
7 purchase totals =	$679.87		$732.4896	$732.48	$732.45	$732.50