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	$64.44	7.399%	$69.2079	$69.21	$69.20	$69.20
Purchase #2	$169.40	5.726%	$179.0998	$179.10	$179.10	$179.10
Purchase #3	$60.48	11.693%	$67.5519	$67.55	$67.55	$67.60
Purchase #4	$38.85	11.863%	$43.4588	$43.46	$43.45	$43.50
Purchase #5	$123.77	6.381%	$131.6678	$131.67	$131.65	$131.70
Purchase #6	$32.93	4.801%	$34.511	$34.51	$34.50	$34.50
Purchase #7	$217.25	11.804%	$242.8942	$242.89	$242.90	$242.90
7 purchase totals =	$707.12		$768.3914	$768.39	$768.35	$768.50