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	$34.31	4.679%	$35.9154	$35.92	$35.90	$35.90
Purchase #2	$239.91	3.318%	$247.8702	$247.87	$247.85	$247.90
Purchase #3	$63.58	6.392%	$67.644	$67.64	$67.65	$67.60
Purchase #4	$211.58	3.256%	$218.469	$218.47	$218.45	$218.50
Purchase #5	$53.76	9.460%	$58.8457	$58.85	$58.85	$58.80
Purchase #6	$168.93	6.528%	$179.9578	$179.96	$179.95	$180.00
Purchase #7	$225.82	13.563%	$256.448	$256.45	$256.45	$256.40
7 purchase totals =	$997.89		$1,065.1501	$1,065.16	$1,065.10	$1,065.10