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	$199.35	12.136%	$223.5431	$223.54	$223.55	$223.50
Purchase #2	$228.44	12.406%	$256.7803	$256.78	$256.80	$256.80
Purchase #3	$239.88	10.453%	$264.9547	$264.95	$264.95	$265.00
Purchase #4	$93.30	12.113%	$104.6014	$104.60	$104.60	$104.60
Purchase #5	$117.74	4.771%	$123.3574	$123.36	$123.35	$123.40
Purchase #6	$40.53	5.578%	$42.7908	$42.79	$42.80	$42.80
Purchase #7	$86.34	12.600%	$97.2188	$97.22	$97.20	$97.20
7 purchase totals =	$1,005.58		$1,113.2465	$1,113.24	$1,113.25	$1,113.30