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	$208.74	4.160%	$217.4236	$217.42	$217.40	$217.40
Purchase #2	$93.64	12.453%	$105.301	$105.30	$105.30	$105.30
Purchase #3	$111.51	8.359%	$120.8311	$120.83	$120.85	$120.80
Purchase #4	$86.26	8.333%	$93.448	$93.45	$93.45	$93.40
Purchase #5	$58.39	7.867%	$62.9835	$62.98	$63.00	$63.00
Purchase #6	$197.72	10.209%	$217.9052	$217.91	$217.90	$217.90
Purchase #7	$222.62	9.437%	$243.6286	$243.63	$243.65	$243.60
7 purchase totals =	$978.88		$1,061.5210	$1,061.52	$1,061.55	$1,061.40