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	$54.43	9.141%	$59.4054	$59.41	$59.40	$59.40
Purchase #2	$159.75	12.802%	$180.2012	$180.20	$180.20	$180.20
Purchase #3	$242.67	13.392%	$275.1684	$275.17	$275.15	$275.20
Purchase #4	$25.41	9.303%	$27.7739	$27.77	$27.75	$27.80
Purchase #5	$128.30	12.850%	$144.7866	$144.79	$144.80	$144.80
Purchase #6	$77.38	8.258%	$83.77	$83.77	$83.75	$83.80
Purchase #7	$250.64	4.848%	$262.791	$262.79	$262.80	$262.80
7 purchase totals =	$938.58		$1,033.8965	$1,033.90	$1,033.85	$1,034.00