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	$89.50	12.773%	$100.9318	$100.93	$100.95	$100.90
Purchase #2	$72.52	7.284%	$77.8024	$77.80	$77.80	$77.80
Purchase #3	$235.30	10.354%	$259.663	$259.66	$259.65	$259.70
Purchase #4	$6.25	10.305%	$6.8941	$6.89	$6.90	$6.90
Purchase #5	$244.39	8.646%	$265.52	$265.52	$265.50	$265.50
Purchase #6	$117.76	13.679%	$133.8684	$133.87	$133.85	$133.90
Purchase #7	$208.88	4.387%	$218.0436	$218.04	$218.05	$218.00
7 purchase totals =	$974.60		$1,062.7233	$1,062.71	$1,062.70	$1,062.70