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	$64.98	12.121%	$72.8562	$72.86	$72.85	$72.90
Purchase #2	$90.69	10.277%	$100.0102	$100.01	$100.00	$100.00
Purchase #3	$29.87	12.526%	$33.6115	$33.61	$33.60	$33.60
Purchase #4	$94.98	13.153%	$107.4727	$107.47	$107.45	$107.50
Purchase #5	$167.69	10.259%	$184.8933	$184.89	$184.90	$184.90
Purchase #6	$165.77	3.501%	$171.5736	$171.57	$171.55	$171.60
Purchase #7	$239.98	8.622%	$260.6711	$260.67	$260.65	$260.70
7 purchase totals =	$853.96		$931.0886	$931.08	$931.00	$931.20