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	$78.39	8.339%	$84.9269	$84.93	$84.95	$84.90
Purchase #2	$153.27	7.196%	$164.2993	$164.30	$164.30	$164.30
Purchase #3	$82.82	8.314%	$89.7057	$89.71	$89.70	$89.70
Purchase #4	$173.86	8.336%	$188.353	$188.35	$188.35	$188.40
Purchase #5	$189.86	13.389%	$215.2804	$215.28	$215.30	$215.30
Purchase #6	$40.49	11.301%	$45.0658	$45.07	$45.05	$45.10
Purchase #7	$138.97	12.488%	$156.3246	$156.32	$156.30	$156.30
7 purchase totals =	$857.66		$943.9557	$943.96	$943.95	$944.00