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	$213.49	10.726%	$236.3889	$236.39	$236.40	$236.40
Purchase #2	$137.71	6.430%	$146.5648	$146.56	$146.55	$146.60
Purchase #3	$168.91	6.408%	$179.7338	$179.73	$179.75	$179.70
Purchase #4	$210.38	4.453%	$219.7482	$219.75	$219.75	$219.70
Purchase #5	$11.47	7.235%	$12.2999	$12.30	$12.30	$12.30
Purchase #6	$229.64	11.729%	$256.5745	$256.57	$256.55	$256.60
Purchase #7	$38.67	10.725%	$42.8174	$42.82	$42.80	$42.80
7 purchase totals =	$1,010.27		$1,094.1275	$1,094.12	$1,094.10	$1,094.10