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	$190.29	13.383%	$215.7565	$215.76	$215.75	$215.80
Purchase #2	$214.34	12.304%	$240.7124	$240.71	$240.70	$240.70
Purchase #3	$170.34	8.872%	$185.4526	$185.45	$185.45	$185.50
Purchase #4	$130.64	13.674%	$148.5037	$148.50	$148.50	$148.50
Purchase #5	$188.74	5.334%	$198.8074	$198.81	$198.80	$198.80
Purchase #6	$163.76	5.411%	$172.6211	$172.62	$172.60	$172.60
Purchase #7	$206.38	4.526%	$215.7208	$215.72	$215.70	$215.70
7 purchase totals =	$1,264.49		$1,377.5745	$1,377.57	$1,377.50	$1,377.60