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	$95.64	11.803%	$106.9284	$106.93	$106.95	$106.90
Purchase #2	$39.85	4.240%	$41.5396	$41.54	$41.55	$41.50
Purchase #3	$83.85	5.564%	$88.5154	$88.52	$88.50	$88.50
Purchase #4	$208.26	6.746%	$222.3092	$222.31	$222.30	$222.30
Purchase #5	$239.83	13.805%	$272.9385	$272.94	$272.95	$272.90
Purchase #6	$80.66	11.425%	$89.8754	$89.88	$89.90	$89.90
Purchase #7	$84.80	3.507%	$87.7739	$87.77	$87.75	$87.80
7 purchase totals =	$832.89		$909.8804	$909.89	$909.90	$909.80