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	$139.61	13.129%	$157.9394	$157.94	$157.95	$157.90
Purchase #2	$222.81	5.412%	$234.8685	$234.87	$234.85	$234.90
Purchase #3	$222.25	9.410%	$243.1637	$243.16	$243.15	$243.20
Purchase #4	$248.36	13.324%	$281.4515	$281.45	$281.45	$281.50
Purchase #5	$127.41	11.870%	$142.5336	$142.53	$142.55	$142.50
Purchase #6	$32.67	7.400%	$35.0876	$35.09	$35.10	$35.10
Purchase #7	$90.92	13.851%	$103.5133	$103.51	$103.50	$103.50
7 purchase totals =	$1,084.03		$1,198.5576	$1,198.55	$1,198.55	$1,198.60