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	$218.40	3.739%	$226.566	$226.57	$226.55	$226.60
Purchase #2	$85.90	9.269%	$93.8621	$93.86	$93.85	$93.90
Purchase #3	$79.28	12.851%	$89.4683	$89.47	$89.45	$89.50
Purchase #4	$17.57	5.156%	$18.4759	$18.48	$18.50	$18.50
Purchase #5	$28.71	3.282%	$29.6523	$29.65	$29.65	$29.70
Purchase #6	$70.37	3.465%	$72.8083	$72.81	$72.80	$72.80
Purchase #7	$64.56	12.472%	$72.6119	$72.61	$72.60	$72.60
7 purchase totals =	$564.79		$603.4448	$603.45	$603.40	$603.60