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	$118.36	4.434%	$123.6081	$123.61	$123.60	$123.60
Purchase #2	$124.96	12.400%	$140.455	$140.46	$140.45	$140.50
Purchase #3	$98.27	3.443%	$101.6534	$101.65	$101.65	$101.70
Purchase #4	$177.76	11.552%	$198.2948	$198.29	$198.30	$198.30
Purchase #5	$209.37	6.677%	$223.3496	$223.35	$223.35	$223.30
Purchase #6	$94.29	8.354%	$102.167	$102.17	$102.15	$102.20
Purchase #7	$218.60	5.161%	$229.8819	$229.88	$229.90	$229.90
7 purchase totals =	$1,041.61		$1,119.4098	$1,119.41	$1,119.40	$1,119.50