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	$55.98	10.319%	$61.7566	$61.76	$61.75	$61.80
Purchase #2	$79.46	4.325%	$82.8966	$82.90	$82.90	$82.90
Purchase #3	$184.29	12.395%	$207.1327	$207.13	$207.15	$207.10
Purchase #4	$181.81	4.763%	$190.4696	$190.47	$190.45	$190.50
Purchase #5	$216.91	3.242%	$223.9422	$223.94	$223.95	$223.90
Purchase #6	$75.61	3.132%	$77.9781	$77.98	$78.00	$78.00
Purchase #7	$75.76	10.360%	$83.6087	$83.61	$83.60	$83.60
7 purchase totals =	$869.82		$927.7845	$927.79	$927.80	$927.80