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	$64.46	13.815%	$73.3651	$73.37	$73.35	$73.40
Purchase #2	$211.99	6.363%	$225.4789	$225.48	$225.50	$225.50
Purchase #3	$171.46	7.491%	$184.3041	$184.30	$184.30	$184.30
Purchase #4	$222.35	8.366%	$240.9518	$240.95	$240.95	$241.00
Purchase #5	$61.65	4.634%	$64.5069	$64.51	$64.50	$64.50
Purchase #6	$247.86	13.232%	$280.6568	$280.66	$280.65	$280.70
Purchase #7	$38.35	11.822%	$42.8837	$42.88	$42.90	$42.90
7 purchase totals =	$1,018.12		$1,112.1473	$1,112.15	$1,112.15	$1,112.30