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	$39.46	5.689%	$41.7049	$41.70	$41.70	$41.70
Purchase #2	$43.43	4.682%	$45.4634	$45.46	$45.45	$45.50
Purchase #3	$68.73	4.775%	$72.0119	$72.01	$72.00	$72.00
Purchase #4	$67.29	10.756%	$74.5277	$74.53	$74.55	$74.50
Purchase #5	$72.95	7.853%	$78.6788	$78.68	$78.70	$78.70
Purchase #6	$198.59	13.652%	$225.7015	$225.70	$225.70	$225.70
Purchase #7	$138.42	6.751%	$147.7647	$147.76	$147.75	$147.80
7 purchase totals =	$628.87		$685.8529	$685.84	$685.85	$685.90