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	$98.67	5.766%	$104.3593	$104.36	$104.35	$104.40
Purchase #2	$57.83	4.307%	$60.3207	$60.32	$60.30	$60.30
Purchase #3	$58.85	5.385%	$62.0191	$62.02	$62.00	$62.00
Purchase #4	$72.35	8.623%	$78.5887	$78.59	$78.60	$78.60
Purchase #5	$164.70	8.514%	$178.7226	$178.72	$178.70	$178.70
Purchase #6	$73.93	6.258%	$78.5565	$78.56	$78.55	$78.60
Purchase #7	$176.56	11.689%	$197.1981	$197.20	$197.20	$197.20
7 purchase totals =	$702.89		$759.7650	$759.77	$759.70	$759.80