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	$124.54	10.263%	$137.3215	$137.32	$137.30	$137.30
Purchase #2	$66.46	9.647%	$72.8714	$72.87	$72.85	$72.90
Purchase #3	$104.56	8.646%	$113.6003	$113.60	$113.60	$113.60
Purchase #4	$226.50	6.327%	$240.8307	$240.83	$240.85	$240.80
Purchase #5	$104.27	13.129%	$117.9596	$117.96	$117.95	$118.00
Purchase #6	$68.31	13.517%	$77.5435	$77.54	$77.55	$77.50
Purchase #7	$244.75	8.456%	$265.4461	$265.45	$265.45	$265.40
7 purchase totals =	$939.39		$1,025.5731	$1,025.57	$1,025.55	$1,025.50