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	$96.47	13.854%	$109.835	$109.84	$109.85	$109.80
Purchase #2	$174.56	5.869%	$184.8049	$184.80	$184.80	$184.80
Purchase #3	$202.96	8.790%	$220.8002	$220.80	$220.80	$220.80
Purchase #4	$174.43	10.338%	$192.4626	$192.46	$192.45	$192.50
Purchase #5	$18.89	6.810%	$20.1764	$20.18	$20.20	$20.20
Purchase #6	$247.92	3.234%	$255.9377	$255.94	$255.95	$255.90
Purchase #7	$107.31	5.726%	$113.4546	$113.45	$113.45	$113.50
7 purchase totals =	$1,022.54		$1,097.4714	$1,097.47	$1,097.50	$1,097.50