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	$65.34	3.207%	$67.4355	$67.44	$67.45	$67.40
Purchase #2	$230.31	6.722%	$245.7914	$245.79	$245.80	$245.80
Purchase #3	$213.67	3.381%	$220.8942	$220.89	$220.90	$220.90
Purchase #4	$91.52	8.805%	$99.5783	$99.58	$99.60	$99.60
Purchase #5	$36.92	5.377%	$38.9052	$38.91	$38.90	$38.90
Purchase #6	$207.84	8.220%	$224.9244	$224.92	$224.90	$224.90
Purchase #7	$201.78	10.204%	$222.3696	$222.37	$222.35	$222.40
7 purchase totals =	$1,047.38		$1,119.8986	$1,119.90	$1,119.90	$1,119.90