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	$231.28	8.198%	$250.2403	$250.24	$250.25	$250.20
Purchase #2	$181.44	3.588%	$187.9501	$187.95	$187.95	$188.00
Purchase #3	$227.43	7.391%	$244.2394	$244.24	$244.25	$244.20
Purchase #4	$38.86	11.301%	$43.2516	$43.25	$43.25	$43.30
Purchase #5	$200.89	11.444%	$223.8799	$223.88	$223.90	$223.90
Purchase #6	$200.34	11.667%	$223.7137	$223.71	$223.70	$223.70
Purchase #7	$233.82	12.141%	$262.2081	$262.21	$262.20	$262.20
7 purchase totals =	$1,314.06		$1,435.4831	$1,435.48	$1,435.50	$1,435.50