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	$51.38	10.561%	$56.8062	$56.81	$56.80	$56.80
Purchase #2	$246.76	11.290%	$274.6192	$274.62	$274.60	$274.60
Purchase #3	$209.63	3.445%	$216.8518	$216.85	$216.85	$216.90
Purchase #4	$51.35	5.870%	$54.3642	$54.36	$54.35	$54.40
Purchase #5	$160.57	7.146%	$172.0443	$172.04	$172.05	$172.00
Purchase #6	$233.97	11.429%	$260.7104	$260.71	$260.70	$260.70
Purchase #7	$56.91	5.331%	$59.9439	$59.94	$59.95	$59.90
7 purchase totals =	$1,010.57		$1,095.3400	$1,095.33	$1,095.30	$1,095.30