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	$86.59	6.682%	$92.3759	$92.38	$92.40	$92.40
Purchase #2	$132.90	8.539%	$144.2483	$144.25	$144.25	$144.20
Purchase #3	$245.65	8.345%	$266.1495	$266.15	$266.15	$266.10
Purchase #4	$124.48	3.419%	$128.736	$128.74	$128.75	$128.70
Purchase #5	$34.25	12.735%	$38.6117	$38.61	$38.60	$38.60
Purchase #6	$232.27	9.105%	$253.4182	$253.42	$253.40	$253.40
Purchase #7	$83.86	6.619%	$89.4107	$89.41	$89.40	$89.40
7 purchase totals =	$940.00		$1,012.9503	$1,012.96	$1,012.95	$1,012.80