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	$60.83	5.778%	$64.3448	$64.34	$64.35	$64.30
Purchase #2	$165.32	10.390%	$182.4967	$182.50	$182.50	$182.50
Purchase #3	$227.74	6.375%	$242.2584	$242.26	$242.25	$242.30
Purchase #4	$121.36	13.196%	$137.3747	$137.37	$137.35	$137.40
Purchase #5	$181.80	3.324%	$187.843	$187.84	$187.85	$187.80
Purchase #6	$164.84	10.801%	$182.6444	$182.64	$182.65	$182.60
Purchase #7	$208.72	6.540%	$222.3703	$222.37	$222.35	$222.40
7 purchase totals =	$1,130.61		$1,219.3323	$1,219.32	$1,219.30	$1,219.30