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	$19.95	3.714%	$20.6909	$20.69	$20.70	$20.70
Purchase #2	$68.60	3.533%	$71.0236	$71.02	$71.00	$71.00
Purchase #3	$177.54	4.715%	$185.911	$185.91	$185.90	$185.90
Purchase #4	$101.55	8.138%	$109.8141	$109.81	$109.80	$109.80
Purchase #5	$250.83	11.713%	$280.2097	$280.21	$280.20	$280.20
Purchase #6	$92.55	3.595%	$95.8772	$95.88	$95.90	$95.90
Purchase #7	$219.69	8.824%	$239.0754	$239.08	$239.10	$239.10
7 purchase totals =	$930.71		$1,002.6019	$1,002.60	$1,002.60	$1,002.60