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	$200.73	12.275%	$225.3696	$225.37	$225.35	$225.40
Purchase #2	$100.88	4.846%	$105.7686	$105.77	$105.75	$105.80
Purchase #3	$82.40	4.298%	$85.9416	$85.94	$85.95	$85.90
Purchase #4	$86.91	9.365%	$95.0491	$95.05	$95.05	$95.00
Purchase #5	$156.87	13.533%	$178.0992	$178.10	$178.10	$178.10
Purchase #6	$181.83	5.521%	$191.8688	$191.87	$191.85	$191.90
Purchase #7	$227.37	10.560%	$251.3803	$251.38	$251.40	$251.40
7 purchase totals =	$1,036.99		$1,133.4772	$1,133.48	$1,133.45	$1,133.50