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	$59.45	7.533%	$63.9284	$63.93	$63.95	$63.90
Purchase #2	$111.38	11.128%	$123.7744	$123.77	$123.75	$123.80
Purchase #3	$195.32	9.334%	$213.5512	$213.55	$213.55	$213.60
Purchase #4	$6.26	7.146%	$6.7073	$6.71	$6.70	$6.70
Purchase #5	$36.66	12.567%	$41.2671	$41.27	$41.25	$41.30
Purchase #6	$79.35	12.760%	$89.4751	$89.48	$89.50	$89.50
Purchase #7	$150.76	13.347%	$170.8819	$170.88	$170.90	$170.90
7 purchase totals =	$639.18		$709.5854	$709.59	$709.60	$709.70