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	$214.82	4.512%	$224.5127	$224.51	$224.50	$224.50
Purchase #2	$159.44	5.341%	$167.9557	$167.96	$167.95	$168.00
Purchase #3	$248.35	3.238%	$256.3916	$256.39	$256.40	$256.40
Purchase #4	$64.73	11.715%	$72.3131	$72.31	$72.30	$72.30
Purchase #5	$205.50	6.220%	$218.2821	$218.28	$218.30	$218.30
Purchase #6	$43.32	7.202%	$46.4399	$46.44	$46.45	$46.40
Purchase #7	$159.66	8.207%	$172.7633	$172.76	$172.75	$172.80
7 purchase totals =	$1,095.82		$1,158.6584	$1,158.65	$1,158.65	$1,158.70