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	$200.25	6.472%	$213.2102	$213.21	$213.20	$213.20
Purchase #2	$196.25	6.167%	$208.3527	$208.35	$208.35	$208.40
Purchase #3	$39.78	13.577%	$45.1809	$45.18	$45.20	$45.20
Purchase #4	$182.57	12.550%	$205.4825	$205.48	$205.50	$205.50
Purchase #5	$221.68	8.670%	$240.8997	$240.90	$240.90	$240.90
Purchase #6	$90.40	4.584%	$94.5439	$94.54	$94.55	$94.50
Purchase #7	$73.94	10.304%	$81.5588	$81.56	$81.55	$81.60
7 purchase totals =	$1,004.87		$1,089.2287	$1,089.22	$1,089.25	$1,089.30