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	$61.48	7.665%	$66.1924	$66.19	$66.20	$66.20
Purchase #2	$93.69	5.748%	$99.0753	$99.08	$99.10	$99.10
Purchase #3	$82.46	12.772%	$92.9918	$92.99	$93.00	$93.00
Purchase #4	$64.74	12.371%	$72.749	$72.75	$72.75	$72.70
Purchase #5	$112.46	9.385%	$123.0144	$123.01	$123.00	$123.00
Purchase #6	$159.65	10.161%	$175.872	$175.87	$175.85	$175.90
Purchase #7	$53.94	10.545%	$59.628	$59.63	$59.65	$59.60
7 purchase totals =	$628.42		$689.5229	$689.52	$689.55	$689.50