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	$113.70	12.162%	$127.5282	$127.53	$127.55	$127.50
Purchase #2	$98.28	3.382%	$101.6038	$101.60	$101.60	$101.60
Purchase #3	$85.90	8.560%	$93.253	$93.25	$93.25	$93.30
Purchase #4	$243.93	8.832%	$265.4739	$265.47	$265.45	$265.50
Purchase #5	$118.86	11.294%	$132.284	$132.28	$132.30	$132.30
Purchase #6	$85.34	9.329%	$93.3014	$93.30	$93.30	$93.30
Purchase #7	$188.61	6.539%	$200.9432	$200.94	$200.95	$200.90
7 purchase totals =	$934.62		$1,014.3875	$1,014.37	$1,014.40	$1,014.40