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	$208.61	11.183%	$231.9389	$231.94	$231.95	$231.90
Purchase #2	$221.99	9.513%	$243.1079	$243.11	$243.10	$243.10
Purchase #3	$9.97	10.441%	$11.011	$11.01	$11.00	$11.00
Purchase #4	$221.85	5.285%	$233.5748	$233.57	$233.55	$233.60
Purchase #5	$51.90	5.531%	$54.7706	$54.77	$54.75	$54.80
Purchase #6	$98.81	3.120%	$101.8929	$101.89	$101.90	$101.90
Purchase #7	$100.67	10.764%	$111.5061	$111.51	$111.50	$111.50
7 purchase totals =	$913.80		$987.8022	$987.80	$987.75	$987.80