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	$28.60	10.826%	$31.6962	$31.70	$31.70	$31.70
Purchase #2	$50.43	7.148%	$54.0347	$54.03	$54.05	$54.00
Purchase #3	$144.42	5.462%	$152.3082	$152.31	$152.30	$152.30
Purchase #4	$153.89	9.621%	$168.6958	$168.70	$168.70	$168.70
Purchase #5	$225.84	13.835%	$257.085	$257.09	$257.10	$257.10
Purchase #6	$158.76	4.498%	$165.901	$165.90	$165.90	$165.90
Purchase #7	$152.62	11.838%	$170.6872	$170.69	$170.70	$170.70
7 purchase totals =	$914.56		$1,000.4081	$1,000.42	$1,000.45	$1,000.40