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	$122.30	6.478%	$130.2226	$130.22	$130.20	$130.20
Purchase #2	$164.58	13.776%	$187.2525	$187.25	$187.25	$187.30
Purchase #3	$72.64	3.262%	$75.0095	$75.01	$75.00	$75.00
Purchase #4	$73.93	6.625%	$78.8279	$78.83	$78.85	$78.80
Purchase #5	$32.42	13.222%	$36.7066	$36.71	$36.70	$36.70
Purchase #6	$206.64	7.754%	$222.6629	$222.66	$222.65	$222.70
Purchase #7	$177.95	10.330%	$196.3322	$196.33	$196.35	$196.30
7 purchase totals =	$850.46		$927.0142	$927.01	$927.00	$927.00