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	$199.67	6.692%	$213.0319	$213.03	$213.05	$213.00
Purchase #2	$28.98	3.147%	$29.892	$29.89	$29.90	$29.90
Purchase #3	$57.93	12.780%	$65.3335	$65.33	$65.35	$65.30
Purchase #4	$58.87	13.710%	$66.9411	$66.94	$66.95	$66.90
Purchase #5	$85.35	3.447%	$88.292	$88.29	$88.30	$88.30
Purchase #6	$32.64	5.691%	$34.4975	$34.50	$34.50	$34.50
Purchase #7	$35.32	7.337%	$37.9114	$37.91	$37.90	$37.90
7 purchase totals =	$498.76		$535.8994	$535.89	$535.95	$535.80