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	$188.53	13.491%	$213.9646	$213.96	$213.95	$214.00
Purchase #2	$25.92	9.452%	$28.37	$28.37	$28.35	$28.40
Purchase #3	$141.32	6.775%	$150.8944	$150.89	$150.90	$150.90
Purchase #4	$83.26	11.791%	$93.0772	$93.08	$93.10	$93.10
Purchase #5	$30.54	7.419%	$32.8058	$32.81	$32.80	$32.80
Purchase #6	$28.96	13.835%	$32.9666	$32.97	$32.95	$33.00
Purchase #7	$80.89	5.401%	$85.2589	$85.26	$85.25	$85.30
7 purchase totals =	$579.42		$637.3375	$637.34	$637.30	$637.50