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	$176.71	10.597%	$195.436	$195.44	$195.45	$195.40
Purchase #2	$139.52	7.823%	$150.4346	$150.43	$150.45	$150.40
Purchase #3	$194.62	10.462%	$214.9811	$214.98	$215.00	$215.00
Purchase #4	$96.69	4.275%	$100.8235	$100.82	$100.80	$100.80
Purchase #5	$31.78	11.780%	$35.5237	$35.52	$35.50	$35.50
Purchase #6	$160.37	13.870%	$182.6133	$182.61	$182.60	$182.60
Purchase #7	$89.87	9.789%	$98.6674	$98.67	$98.65	$98.70
7 purchase totals =	$889.56		$978.4796	$978.47	$978.45	$978.40