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	$66.89	7.480%	$71.8934	$71.89	$71.90	$71.90
Purchase #2	$230.93	5.302%	$243.1739	$243.17	$243.15	$243.20
Purchase #3	$167.53	9.553%	$183.5341	$183.53	$183.55	$183.50
Purchase #4	$52.50	4.334%	$54.7754	$54.78	$54.80	$54.80
Purchase #5	$222.36	5.389%	$234.343	$234.34	$234.35	$234.30
Purchase #6	$27.87	11.615%	$31.1071	$31.11	$31.10	$31.10
Purchase #7	$90.36	7.422%	$97.0665	$97.07	$97.05	$97.10
7 purchase totals =	$858.44		$915.8934	$915.89	$915.90	$915.90