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	$29.37	12.626%	$33.0783	$33.08	$33.10	$33.10
Purchase #2	$217.85	9.813%	$239.2276	$239.23	$239.25	$239.20
Purchase #3	$45.77	6.835%	$48.8984	$48.90	$48.90	$48.90
Purchase #4	$150.67	10.512%	$166.5084	$166.51	$166.50	$166.50
Purchase #5	$186.47	5.203%	$196.172	$196.17	$196.15	$196.20
Purchase #6	$216.29	3.137%	$223.075	$223.08	$223.10	$223.10
Purchase #7	$94.50	11.170%	$105.0557	$105.06	$105.05	$105.10
7 purchase totals =	$940.92		$1,012.0154	$1,012.03	$1,012.05	$1,012.10