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	$219.90	5.738%	$232.5179	$232.52	$232.50	$232.50
Purchase #2	$236.94	8.232%	$256.4449	$256.44	$256.45	$256.40
Purchase #3	$176.26	9.206%	$192.4865	$192.49	$192.50	$192.50
Purchase #4	$70.31	3.486%	$72.761	$72.76	$72.75	$72.80
Purchase #5	$242.37	11.238%	$269.6075	$269.61	$269.60	$269.60
Purchase #6	$18.69	7.676%	$20.1246	$20.12	$20.10	$20.10
Purchase #7	$27.86	12.247%	$31.272	$31.27	$31.25	$31.30
7 purchase totals =	$992.33		$1,075.2144	$1,075.21	$1,075.15	$1,075.20