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	$190.26	13.330%	$215.6217	$215.62	$215.60	$215.60
Purchase #2	$225.59	10.635%	$249.5815	$249.58	$249.60	$249.60
Purchase #3	$100.26	8.625%	$108.9074	$108.91	$108.90	$108.90
Purchase #4	$183.43	7.173%	$196.5874	$196.59	$196.60	$196.60
Purchase #5	$164.50	13.468%	$186.6549	$186.65	$186.65	$186.70
Purchase #6	$7.29	13.731%	$8.291	$8.29	$8.30	$8.30
Purchase #7	$142.74	5.759%	$150.9604	$150.96	$150.95	$151.00
7 purchase totals =	$1,014.07		$1,116.6043	$1,116.60	$1,116.60	$1,116.70