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	$104.95	9.503%	$114.9234	$114.92	$114.90	$114.90
Purchase #2	$18.82	12.230%	$21.1217	$21.12	$21.10	$21.10
Purchase #3	$40.66	10.855%	$45.0736	$45.07	$45.05	$45.10
Purchase #4	$77.99	13.706%	$88.6793	$88.68	$88.70	$88.70
Purchase #5	$78.93	10.819%	$87.4694	$87.47	$87.45	$87.50
Purchase #6	$25.90	9.570%	$28.3786	$28.38	$28.40	$28.40
Purchase #7	$89.42	12.137%	$100.2729	$100.27	$100.25	$100.30
7 purchase totals =	$436.67		$485.9189	$485.91	$485.85	$486.00