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	$172.63	7.216%	$185.087	$185.09	$185.10	$185.10
Purchase #2	$95.30	12.578%	$107.2868	$107.29	$107.30	$107.30
Purchase #3	$92.45	6.549%	$98.5046	$98.50	$98.50	$98.50
Purchase #4	$157.90	10.834%	$175.0069	$175.01	$175.00	$175.00
Purchase #5	$131.93	6.234%	$140.1545	$140.15	$140.15	$140.20
Purchase #6	$244.46	10.425%	$269.945	$269.95	$269.95	$269.90
Purchase #7	$118.92	3.832%	$123.477	$123.48	$123.50	$123.50
7 purchase totals =	$1,013.59		$1,099.4618	$1,099.47	$1,099.50	$1,099.50