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	$196.74	13.213%	$222.7353	$222.74	$222.75	$222.70
Purchase #2	$156.58	9.349%	$171.2187	$171.22	$171.20	$171.20
Purchase #3	$107.30	6.228%	$113.9826	$113.98	$114.00	$114.00
Purchase #4	$134.59	5.769%	$142.3545	$142.35	$142.35	$142.40
Purchase #5	$135.79	12.172%	$152.3184	$152.32	$152.30	$152.30
Purchase #6	$146.86	9.670%	$161.0614	$161.06	$161.05	$161.10
Purchase #7	$248.85	6.676%	$265.4632	$265.46	$265.45	$265.50
7 purchase totals =	$1,126.71		$1,229.1341	$1,229.13	$1,229.10	$1,229.20