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	$236.47	4.595%	$247.3358	$247.34	$247.35	$247.30
Purchase #2	$11.80	11.542%	$13.162	$13.16	$13.15	$13.20
Purchase #3	$108.84	4.582%	$113.827	$113.83	$113.85	$113.80
Purchase #4	$242.69	8.408%	$263.0954	$263.10	$263.10	$263.10
Purchase #5	$92.57	6.580%	$98.6611	$98.66	$98.65	$98.70
Purchase #6	$85.82	5.870%	$90.8576	$90.86	$90.85	$90.90
Purchase #7	$102.32	13.679%	$116.3164	$116.32	$116.30	$116.30
7 purchase totals =	$880.51		$943.2553	$943.27	$943.25	$943.30