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	$50.82	12.776%	$57.3128	$57.31	$57.30	$57.30
Purchase #2	$236.57	12.288%	$265.6397	$265.64	$265.65	$265.60
Purchase #3	$63.71	4.819%	$66.7802	$66.78	$66.80	$66.80
Purchase #4	$215.36	8.561%	$233.797	$233.80	$233.80	$233.80
Purchase #5	$154.57	8.838%	$168.2309	$168.23	$168.25	$168.20
Purchase #6	$97.65	8.133%	$105.5919	$105.59	$105.60	$105.60
Purchase #7	$234.56	5.365%	$247.1441	$247.14	$247.15	$247.10
7 purchase totals =	$1,053.24		$1,144.4966	$1,144.49	$1,144.55	$1,144.40