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	$212.39	4.740%	$222.4573	$222.46	$222.45	$222.50
Purchase #2	$129.57	9.193%	$141.4814	$141.48	$141.50	$141.50
Purchase #3	$148.46	6.526%	$158.1485	$158.15	$158.15	$158.10
Purchase #4	$58.57	12.400%	$65.8327	$65.83	$65.85	$65.80
Purchase #5	$91.76	13.874%	$104.4908	$104.49	$104.50	$104.50
Purchase #6	$64.69	4.781%	$67.7828	$67.78	$67.80	$67.80
Purchase #7	$150.39	5.676%	$158.9261	$158.93	$158.95	$158.90
7 purchase totals =	$855.83		$919.1196	$919.12	$919.20	$919.10