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	$78.62	9.335%	$85.9592	$85.96	$85.95	$86.00
Purchase #2	$164.90	10.849%	$182.79	$182.79	$182.80	$182.80
Purchase #3	$147.74	13.275%	$167.3525	$167.35	$167.35	$167.40
Purchase #4	$229.62	9.472%	$251.3696	$251.37	$251.35	$251.40
Purchase #5	$16.89	3.718%	$17.518	$17.52	$17.50	$17.50
Purchase #6	$248.29	12.792%	$280.0513	$280.05	$280.05	$280.10
Purchase #7	$19.57	3.626%	$20.2796	$20.28	$20.30	$20.30
7 purchase totals =	$905.63		$1,005.3202	$1,005.32	$1,005.30	$1,005.50