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	$198.27	3.562%	$205.3324	$205.33	$205.35	$205.30
Purchase #2	$161.42	3.274%	$166.7049	$166.70	$166.70	$166.70
Purchase #3	$40.88	5.333%	$43.0601	$43.06	$43.05	$43.10
Purchase #4	$166.58	7.842%	$179.6432	$179.64	$179.65	$179.60
Purchase #5	$72.41	8.686%	$78.6995	$78.70	$78.70	$78.70
Purchase #6	$33.37	4.564%	$34.893	$34.89	$34.90	$34.90
Purchase #7	$45.34	11.728%	$50.6575	$50.66	$50.65	$50.70
7 purchase totals =	$718.27		$758.9906	$758.98	$759.00	$759.00