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	$183.56	8.483%	$199.1314	$199.13	$199.15	$199.10
Purchase #2	$38.30	5.645%	$40.462	$40.46	$40.45	$40.50
Purchase #3	$149.92	13.119%	$169.588	$169.59	$169.60	$169.60
Purchase #4	$116.43	12.844%	$131.3843	$131.38	$131.40	$131.40
Purchase #5	$241.97	13.181%	$273.8641	$273.86	$273.85	$273.90
Purchase #6	$108.77	4.167%	$113.3024	$113.30	$113.30	$113.30
Purchase #7	$44.65	10.656%	$49.4079	$49.41	$49.40	$49.40
7 purchase totals =	$883.60		$977.1401	$977.13	$977.15	$977.20