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	$199.90	6.727%	$213.3473	$213.35	$213.35	$213.30
Purchase #2	$118.80	10.144%	$130.8511	$130.85	$130.85	$130.90
Purchase #3	$132.34	3.207%	$136.5841	$136.58	$136.60	$136.60
Purchase #4	$189.31	3.833%	$196.5663	$196.57	$196.55	$196.60
Purchase #5	$197.27	12.315%	$221.5638	$221.56	$221.55	$221.60
Purchase #6	$187.32	5.126%	$196.922	$196.92	$196.90	$196.90
Purchase #7	$147.87	6.587%	$157.6102	$157.61	$157.60	$157.60
7 purchase totals =	$1,172.81		$1,253.4448	$1,253.44	$1,253.40	$1,253.50