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	$95.55	9.410%	$104.5413	$104.54	$104.55	$104.50
Purchase #2	$222.44	10.288%	$245.3246	$245.32	$245.30	$245.30
Purchase #3	$90.65	10.597%	$100.2562	$100.26	$100.25	$100.30
Purchase #4	$42.43	6.198%	$45.0598	$45.06	$45.05	$45.10
Purchase #5	$82.49	4.703%	$86.3695	$86.37	$86.35	$86.40
Purchase #6	$143.68	12.632%	$161.8297	$161.83	$161.85	$161.80
Purchase #7	$152.94	13.675%	$173.8545	$173.85	$173.85	$173.90
7 purchase totals =	$830.18		$917.2356	$917.23	$917.20	$917.30