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	$106.44	9.660%	$116.7221	$116.72	$116.70	$116.70
Purchase #2	$103.91	12.669%	$117.0744	$117.07	$117.05	$117.10
Purchase #3	$55.61	5.164%	$58.4817	$58.48	$58.50	$58.50
Purchase #4	$125.85	10.802%	$139.4443	$139.44	$139.45	$139.40
Purchase #5	$181.32	9.816%	$199.1184	$199.12	$199.10	$199.10
Purchase #6	$192.83	10.766%	$213.5901	$213.59	$213.60	$213.60
Purchase #7	$149.38	12.408%	$167.9151	$167.92	$167.90	$167.90
7 purchase totals =	$915.34		$1,012.3461	$1,012.34	$1,012.30	$1,012.30