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	$86.95	10.870%	$96.4015	$96.40	$96.40	$96.40
Purchase #2	$53.94	12.799%	$60.8438	$60.84	$60.85	$60.80
Purchase #3	$78.68	10.810%	$87.1853	$87.19	$87.20	$87.20
Purchase #4	$59.60	12.260%	$66.907	$66.91	$66.90	$66.90
Purchase #5	$36.25	11.715%	$40.4967	$40.50	$40.50	$40.50
Purchase #6	$224.86	9.158%	$245.4527	$245.45	$245.45	$245.50
Purchase #7	$10.61	11.654%	$11.8465	$11.85	$11.85	$11.80
7 purchase totals =	$550.89		$609.1335	$609.14	$609.15	$609.10