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	$241.87	13.123%	$273.6106	$273.61	$273.60	$273.60
Purchase #2	$104.75	9.287%	$114.4781	$114.48	$114.50	$114.50
Purchase #3	$11.76	9.383%	$12.8634	$12.86	$12.85	$12.90
Purchase #4	$178.39	12.562%	$200.7994	$200.80	$200.80	$200.80
Purchase #5	$62.77	13.284%	$71.1084	$71.11	$71.10	$71.10
Purchase #6	$55.57	6.148%	$58.9864	$58.99	$59.00	$59.00
Purchase #7	$211.29	12.484%	$237.6674	$237.67	$237.65	$237.70
7 purchase totals =	$866.40		$969.5137	$969.52	$969.50	$969.60