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	$196.96	12.173%	$220.9359	$220.94	$220.95	$220.90
Purchase #2	$19.44	12.626%	$21.8945	$21.89	$21.90	$21.90
Purchase #3	$196.67	13.273%	$222.774	$222.77	$222.75	$222.80
Purchase #4	$134.71	4.114%	$140.252	$140.25	$140.25	$140.30
Purchase #5	$30.40	12.398%	$34.169	$34.17	$34.15	$34.20
Purchase #6	$201.41	13.535%	$228.6708	$228.67	$228.65	$228.70
Purchase #7	$96.75	13.523%	$109.8335	$109.83	$109.85	$109.80
7 purchase totals =	$876.34		$978.5297	$978.52	$978.50	$978.60