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	$34.97	6.172%	$37.1283	$37.13	$37.15	$37.10
Purchase #2	$132.99	13.734%	$151.2548	$151.25	$151.25	$151.30
Purchase #3	$5.86	8.638%	$6.3662	$6.37	$6.35	$6.40
Purchase #4	$218.41	13.390%	$247.6551	$247.66	$247.65	$247.70
Purchase #5	$83.35	11.364%	$92.8219	$92.82	$92.80	$92.80
Purchase #6	$233.86	5.386%	$246.4557	$246.46	$246.45	$246.50
Purchase #7	$202.94	9.341%	$221.8966	$221.90	$221.90	$221.90
7 purchase totals =	$912.38		$1,003.5786	$1,003.59	$1,003.55	$1,003.70