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	$105.66	10.538%	$116.7945	$116.79	$116.80	$116.80
Purchase #2	$95.79	4.807%	$100.3946	$100.39	$100.40	$100.40
Purchase #3	$233.58	10.410%	$257.8957	$257.90	$257.90	$257.90
Purchase #4	$13.60	10.119%	$14.9762	$14.98	$15.00	$15.00
Purchase #5	$122.56	11.383%	$136.511	$136.51	$136.50	$136.50
Purchase #6	$190.32	11.417%	$212.0488	$212.05	$212.05	$212.00
Purchase #7	$83.96	6.350%	$89.2915	$89.29	$89.30	$89.30
7 purchase totals =	$845.47		$927.9123	$927.91	$927.95	$927.90