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	$200.78	7.707%	$216.2541	$216.25	$216.25	$216.30
Purchase #2	$174.80	4.222%	$182.1801	$182.18	$182.20	$182.20
Purchase #3	$223.90	10.391%	$247.1654	$247.17	$247.15	$247.20
Purchase #4	$108.98	7.802%	$117.4826	$117.48	$117.50	$117.50
Purchase #5	$89.98	7.329%	$96.5746	$96.57	$96.55	$96.60
Purchase #6	$212.43	12.708%	$239.4256	$239.43	$239.45	$239.40
Purchase #7	$28.66	12.440%	$32.2253	$32.23	$32.25	$32.20
7 purchase totals =	$1,039.53		$1,131.3077	$1,131.31	$1,131.35	$1,131.40