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	$241.74	5.372%	$254.7263	$254.73	$254.75	$254.70
Purchase #2	$213.30	8.449%	$231.3217	$231.32	$231.30	$231.30
Purchase #3	$195.48	11.562%	$218.0814	$218.08	$218.10	$218.10
Purchase #4	$192.42	9.768%	$211.2156	$211.22	$211.20	$211.20
Purchase #5	$63.81	13.381%	$72.3484	$72.35	$72.35	$72.30
Purchase #6	$220.89	10.296%	$243.6328	$243.63	$243.65	$243.60
Purchase #7	$123.86	3.594%	$128.3115	$128.31	$128.30	$128.30
7 purchase totals =	$1,251.50		$1,359.6377	$1,359.64	$1,359.65	$1,359.50