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	$78.92	5.815%	$83.5092	$83.51	$83.50	$83.50
Purchase #2	$140.50	6.790%	$150.04	$150.04	$150.05	$150.00
Purchase #3	$170.89	8.427%	$185.2909	$185.29	$185.30	$185.30
Purchase #4	$85.52	9.431%	$93.5854	$93.59	$93.60	$93.60
Purchase #5	$93.66	12.401%	$105.2748	$105.27	$105.25	$105.30
Purchase #6	$240.82	10.153%	$265.2705	$265.27	$265.25	$265.30
Purchase #7	$152.80	7.659%	$164.503	$164.50	$164.50	$164.50
7 purchase totals =	$963.11		$1,047.4738	$1,047.47	$1,047.45	$1,047.50