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	$217.63	9.642%	$238.6139	$238.61	$238.60	$238.60
Purchase #2	$159.55	8.162%	$172.5725	$172.57	$172.55	$172.60
Purchase #3	$179.72	8.547%	$195.0807	$195.08	$195.10	$195.10
Purchase #4	$82.58	9.596%	$90.5044	$90.50	$90.50	$90.50
Purchase #5	$70.86	11.363%	$78.9118	$78.91	$78.90	$78.90
Purchase #6	$245.29	11.358%	$273.15	$273.15	$273.15	$273.20
Purchase #7	$33.74	12.790%	$38.0553	$38.06	$38.05	$38.10
7 purchase totals =	$989.37		$1,086.8886	$1,086.88	$1,086.85	$1,087.00