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	$189.27	12.555%	$213.0328	$213.03	$213.05	$213.00
Purchase #2	$43.60	4.120%	$45.3963	$45.40	$45.40	$45.40
Purchase #3	$77.66	10.337%	$85.6877	$85.69	$85.70	$85.70
Purchase #4	$122.77	11.363%	$136.7204	$136.72	$136.70	$136.70
Purchase #5	$86.77	3.391%	$89.7124	$89.71	$89.70	$89.70
Purchase #6	$157.30	8.840%	$171.2053	$171.21	$171.20	$171.20
Purchase #7	$250.85	3.255%	$259.0152	$259.02	$259.00	$259.00
7 purchase totals =	$928.22		$1,000.7701	$1,000.78	$1,000.75	$1,000.70