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	$139.66	8.497%	$151.5269	$151.53	$151.55	$151.50
Purchase #2	$64.34	11.240%	$71.5718	$71.57	$71.55	$71.60
Purchase #3	$215.68	9.286%	$235.708	$235.71	$235.70	$235.70
Purchase #4	$89.25	12.472%	$100.3813	$100.38	$100.40	$100.40
Purchase #5	$95.88	5.285%	$100.9473	$100.95	$100.95	$100.90
Purchase #6	$189.78	13.387%	$215.1858	$215.19	$215.20	$215.20
Purchase #7	$166.47	7.869%	$179.5695	$179.57	$179.55	$179.60
7 purchase totals =	$961.06		$1,054.8906	$1,054.90	$1,054.90	$1,054.90