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	$59.88	5.870%	$63.395	$63.40	$63.40	$63.40
Purchase #2	$63.43	7.603%	$68.2526	$68.25	$68.25	$68.30
Purchase #3	$211.43	5.424%	$222.898	$222.90	$222.90	$222.90
Purchase #4	$218.57	3.139%	$225.4309	$225.43	$225.45	$225.40
Purchase #5	$160.69	6.312%	$170.8328	$170.83	$170.85	$170.80
Purchase #6	$53.65	3.373%	$55.4596	$55.46	$55.45	$55.50
Purchase #7	$165.89	10.167%	$182.756	$182.76	$182.75	$182.80
7 purchase totals =	$933.54		$989.0249	$989.03	$989.05	$989.10