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	$63.34	12.652%	$71.3538	$71.35	$71.35	$71.40
Purchase #2	$247.53	3.216%	$255.4906	$255.49	$255.50	$255.50
Purchase #3	$77.92	11.637%	$86.9876	$86.99	$87.00	$87.00
Purchase #4	$213.77	10.581%	$236.389	$236.39	$236.40	$236.40
Purchase #5	$73.68	11.458%	$82.1223	$82.12	$82.10	$82.10
Purchase #6	$9.55	13.691%	$10.8575	$10.86	$10.85	$10.90
Purchase #7	$151.61	13.301%	$171.7756	$171.78	$171.80	$171.80
7 purchase totals =	$837.40		$914.9764	$914.98	$915.00	$915.10