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	$68.32	4.823%	$71.6151	$71.62	$71.60	$71.60
Purchase #2	$40.79	11.809%	$45.6069	$45.61	$45.60	$45.60
Purchase #3	$108.54	10.262%	$119.6784	$119.68	$119.70	$119.70
Purchase #4	$168.82	10.778%	$187.0154	$187.02	$187.00	$187.00
Purchase #5	$46.85	5.169%	$49.2717	$49.27	$49.25	$49.30
Purchase #6	$86.53	5.727%	$91.4856	$91.49	$91.50	$91.50
Purchase #7	$232.56	10.442%	$256.8439	$256.84	$256.85	$256.80
7 purchase totals =	$752.41		$821.5170	$821.53	$821.50	$821.50