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	$200.59	10.567%	$221.7863	$221.79	$221.80	$221.80
Purchase #2	$10.44	10.366%	$11.5222	$11.52	$11.50	$11.50
Purchase #3	$79.94	13.682%	$90.8774	$90.88	$90.90	$90.90
Purchase #4	$249.25	6.711%	$265.9772	$265.98	$266.00	$266.00
Purchase #5	$37.94	11.415%	$42.2709	$42.27	$42.25	$42.30
Purchase #6	$209.38	6.400%	$222.7803	$222.78	$222.80	$222.80
Purchase #7	$213.47	8.398%	$231.3972	$231.40	$231.40	$231.40
7 purchase totals =	$1,001.01		$1,086.6115	$1,086.62	$1,086.65	$1,086.70