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	$200.68	12.604%	$225.9737	$225.97	$225.95	$226.00
Purchase #2	$250.58	9.163%	$273.5406	$273.54	$273.55	$273.50
Purchase #3	$37.66	13.505%	$42.746	$42.75	$42.75	$42.70
Purchase #4	$9.64	9.839%	$10.5885	$10.59	$10.60	$10.60
Purchase #5	$176.77	13.400%	$200.4572	$200.46	$200.45	$200.50
Purchase #6	$212.97	9.650%	$233.5216	$233.52	$233.50	$233.50
Purchase #7	$88.66	6.857%	$94.7394	$94.74	$94.75	$94.70
7 purchase totals =	$976.96		$1,081.5670	$1,081.57	$1,081.55	$1,081.50