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	$163.70	3.332%	$169.1545	$169.15	$169.15	$169.20
Purchase #2	$166.71	10.473%	$184.1695	$184.17	$184.15	$184.20
Purchase #3	$219.47	10.666%	$242.8787	$242.88	$242.90	$242.90
Purchase #4	$107.72	9.495%	$117.948	$117.95	$117.95	$117.90
Purchase #5	$75.81	6.657%	$80.8567	$80.86	$80.85	$80.90
Purchase #6	$168.43	13.418%	$191.0299	$191.03	$191.05	$191.00
Purchase #7	$80.57	12.688%	$90.7927	$90.79	$90.80	$90.80
7 purchase totals =	$982.41		$1,076.8300	$1,076.83	$1,076.85	$1,076.90