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	$31.48	10.442%	$34.7671	$34.77	$34.75	$34.80
Purchase #2	$212.38	5.322%	$223.6829	$223.68	$223.70	$223.70
Purchase #3	$80.33	10.857%	$89.0514	$89.05	$89.05	$89.10
Purchase #4	$87.78	4.249%	$91.5098	$91.51	$91.50	$91.50
Purchase #5	$69.82	10.577%	$77.2049	$77.20	$77.20	$77.20
Purchase #6	$93.38	10.192%	$102.8973	$102.90	$102.90	$102.90
Purchase #7	$227.27	13.711%	$258.431	$258.43	$258.45	$258.40
7 purchase totals =	$802.44		$877.5444	$877.54	$877.55	$877.60