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	$222.83	3.149%	$229.8469	$229.85	$229.85	$229.80
Purchase #2	$199.26	10.596%	$220.3736	$220.37	$220.35	$220.40
Purchase #3	$83.30	7.213%	$89.3084	$89.31	$89.30	$89.30
Purchase #4	$207.54	5.306%	$218.5521	$218.55	$218.55	$218.60
Purchase #5	$127.63	7.818%	$137.6081	$137.61	$137.60	$137.60
Purchase #6	$30.58	5.622%	$32.2992	$32.30	$32.30	$32.30
Purchase #7	$119.78	3.170%	$123.577	$123.58	$123.60	$123.60
7 purchase totals =	$990.92		$1,051.5653	$1,051.57	$1,051.55	$1,051.60