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	$238.26	11.181%	$264.8999	$264.90	$264.90	$264.90
Purchase #2	$161.48	3.841%	$167.6824	$167.68	$167.70	$167.70
Purchase #3	$203.75	11.668%	$227.5236	$227.52	$227.50	$227.50
Purchase #4	$35.62	6.772%	$38.0322	$38.03	$38.05	$38.00
Purchase #5	$241.45	7.789%	$260.2565	$260.26	$260.25	$260.30
Purchase #6	$211.42	4.479%	$220.8895	$220.89	$220.90	$220.90
Purchase #7	$54.78	8.170%	$59.2555	$59.26	$59.25	$59.30
7 purchase totals =	$1,146.76		$1,238.5396	$1,238.54	$1,238.55	$1,238.60