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	$200.97	5.161%	$211.3421	$211.34	$211.35	$211.30
Purchase #2	$42.27	10.606%	$46.7532	$46.75	$46.75	$46.80
Purchase #3	$87.67	11.498%	$97.7503	$97.75	$97.75	$97.80
Purchase #4	$80.66	11.464%	$89.9069	$89.91	$89.90	$89.90
Purchase #5	$91.76	12.778%	$103.4851	$103.49	$103.50	$103.50
Purchase #6	$139.90	4.270%	$145.8737	$145.87	$145.85	$145.90
Purchase #7	$112.76	3.259%	$116.4348	$116.43	$116.45	$116.40
7 purchase totals =	$755.99		$811.5461	$811.54	$811.55	$811.60