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	$215.75	5.233%	$227.0402	$227.04	$227.05	$227.00
Purchase #2	$88.50	12.350%	$99.4298	$99.43	$99.45	$99.40
Purchase #3	$37.88	7.413%	$40.688	$40.69	$40.70	$40.70
Purchase #4	$43.70	9.760%	$47.9651	$47.97	$47.95	$48.00
Purchase #5	$124.89	10.110%	$137.5164	$137.52	$137.50	$137.50
Purchase #6	$179.38	8.295%	$194.2596	$194.26	$194.25	$194.30
Purchase #7	$97.66	13.668%	$111.0082	$111.01	$111.00	$111.00
7 purchase totals =	$787.76		$857.9073	$857.92	$857.90	$857.90