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	$69.76	11.219%	$77.5864	$77.59	$77.60	$77.60
Purchase #2	$148.27	6.396%	$157.7533	$157.75	$157.75	$157.80
Purchase #3	$59.50	5.816%	$62.9605	$62.96	$62.95	$63.00
Purchase #4	$7.53	4.483%	$7.8676	$7.87	$7.85	$7.90
Purchase #5	$39.35	5.238%	$41.4112	$41.41	$41.40	$41.40
Purchase #6	$125.54	11.208%	$139.6105	$139.61	$139.60	$139.60
Purchase #7	$205.59	9.778%	$225.6926	$225.69	$225.70	$225.70
7 purchase totals =	$655.54		$712.8821	$712.88	$712.85	$713.00