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	$162.95	9.570%	$178.5443	$178.54	$178.55	$178.50
Purchase #2	$247.33	3.532%	$256.0657	$256.07	$256.05	$256.10
Purchase #3	$142.28	5.477%	$150.0727	$150.07	$150.05	$150.10
Purchase #4	$139.29	6.518%	$148.3689	$148.37	$148.35	$148.40
Purchase #5	$123.87	12.646%	$139.5346	$139.53	$139.55	$139.50
Purchase #6	$85.47	7.832%	$92.164	$92.16	$92.15	$92.20
Purchase #7	$180.56	12.256%	$202.6894	$202.69	$202.70	$202.70
7 purchase totals =	$1,081.75		$1,167.4396	$1,167.43	$1,167.40	$1,167.50