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	$55.68	5.340%	$58.6533	$58.65	$58.65	$58.70
Purchase #2	$62.61	7.257%	$67.1536	$67.15	$67.15	$67.20
Purchase #3	$225.46	4.387%	$235.3509	$235.35	$235.35	$235.40
Purchase #4	$36.54	11.642%	$40.794	$40.79	$40.80	$40.80
Purchase #5	$165.77	5.422%	$174.758	$174.76	$174.75	$174.80
Purchase #6	$116.82	8.742%	$127.0324	$127.03	$127.05	$127.00
Purchase #7	$238.57	6.113%	$253.1538	$253.15	$253.15	$253.20
7 purchase totals =	$901.45		$956.8960	$956.88	$956.90	$957.10