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	$29.63	12.743%	$33.4058	$33.41	$33.40	$33.40
Purchase #2	$53.33	11.323%	$59.3686	$59.37	$59.35	$59.40
Purchase #3	$181.91	8.861%	$198.029	$198.03	$198.05	$198.00
Purchase #4	$41.60	4.596%	$43.5119	$43.51	$43.50	$43.50
Purchase #5	$63.31	3.717%	$65.6632	$65.66	$65.65	$65.70
Purchase #6	$146.58	13.395%	$166.2144	$166.21	$166.20	$166.20
Purchase #7	$124.85	5.271%	$131.4308	$131.43	$131.45	$131.40
7 purchase totals =	$641.21		$697.6237	$697.62	$697.60	$697.60