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	$196.43	8.698%	$213.5155	$213.52	$213.50	$213.50
Purchase #2	$6.30	9.361%	$6.8897	$6.89	$6.90	$6.90
Purchase #3	$175.35	12.548%	$197.3529	$197.35	$197.35	$197.40
Purchase #4	$96.43	12.414%	$108.4008	$108.40	$108.40	$108.40
Purchase #5	$94.42	5.788%	$99.885	$99.89	$99.90	$99.90
Purchase #6	$24.84	10.460%	$27.4383	$27.44	$27.45	$27.40
Purchase #7	$227.95	12.210%	$255.7827	$255.78	$255.80	$255.80
7 purchase totals =	$821.72		$909.2649	$909.27	$909.30	$909.30