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	$114.83	3.103%	$118.3932	$118.39	$118.40	$118.40
Purchase #2	$128.40	9.330%	$140.3797	$140.38	$140.40	$140.40
Purchase #3	$22.31	9.490%	$24.4272	$24.43	$24.45	$24.40
Purchase #4	$119.71	3.334%	$123.7011	$123.70	$123.70	$123.70
Purchase #5	$250.78	9.151%	$273.7289	$273.73	$273.75	$273.70
Purchase #6	$12.51	13.214%	$14.1631	$14.16	$14.15	$14.20
Purchase #7	$45.83	10.109%	$50.463	$50.46	$50.45	$50.50
7 purchase totals =	$694.37		$745.2562	$745.25	$745.30	$745.30