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	$61.75	9.137%	$67.3921	$67.39	$67.40	$67.40
Purchase #2	$191.27	11.417%	$213.1073	$213.11	$213.10	$213.10
Purchase #3	$55.31	5.321%	$58.253	$58.25	$58.25	$58.30
Purchase #4	$233.86	12.870%	$263.9578	$263.96	$263.95	$264.00
Purchase #5	$172.57	8.601%	$187.4127	$187.41	$187.40	$187.40
Purchase #6	$243.25	9.298%	$265.8674	$265.87	$265.85	$265.90
Purchase #7	$107.59	4.577%	$112.5144	$112.51	$112.50	$112.50
7 purchase totals =	$1,065.60		$1,168.5047	$1,168.50	$1,168.45	$1,168.60