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	$130.28	8.862%	$141.8254	$141.83	$141.85	$141.80
Purchase #2	$82.73	8.615%	$89.8572	$89.86	$89.85	$89.90
Purchase #3	$68.80	13.861%	$78.3364	$78.34	$78.35	$78.30
Purchase #4	$155.68	10.379%	$171.838	$171.84	$171.85	$171.80
Purchase #5	$69.90	8.380%	$75.7576	$75.76	$75.75	$75.80
Purchase #6	$47.47	13.840%	$54.0398	$54.04	$54.05	$54.00
Purchase #7	$112.39	6.570%	$119.774	$119.77	$119.75	$119.80
7 purchase totals =	$667.25		$731.4284	$731.44	$731.45	$731.40