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	$47.46	13.572%	$53.9013	$53.90	$53.90	$53.90
Purchase #2	$220.86	8.296%	$239.1825	$239.18	$239.20	$239.20
Purchase #3	$216.85	11.268%	$241.2847	$241.28	$241.30	$241.30
Purchase #4	$207.86	13.405%	$235.7236	$235.72	$235.70	$235.70
Purchase #5	$55.98	3.188%	$57.7646	$57.76	$57.75	$57.80
Purchase #6	$125.70	4.264%	$131.0598	$131.06	$131.05	$131.10
Purchase #7	$64.41	11.778%	$71.9962	$72.00	$72.00	$72.00
7 purchase totals =	$939.12		$1,030.9127	$1,030.90	$1,030.90	$1,031.00