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	$57.83	6.179%	$61.4033	$61.40	$61.40	$61.40
Purchase #2	$139.46	12.176%	$156.4406	$156.44	$156.45	$156.40
Purchase #3	$141.49	13.365%	$160.4001	$160.40	$160.40	$160.40
Purchase #4	$233.30	13.522%	$264.8468	$264.85	$264.85	$264.80
Purchase #5	$72.90	4.282%	$76.0216	$76.02	$76.00	$76.00
Purchase #6	$65.29	8.307%	$70.7136	$70.71	$70.70	$70.70
Purchase #7	$217.55	4.197%	$226.6806	$226.68	$226.70	$226.70
7 purchase totals =	$927.82		$1,016.5066	$1,016.50	$1,016.50	$1,016.40