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	$53.53	7.281%	$57.4275	$57.43	$57.45	$57.40
Purchase #2	$24.63	11.709%	$27.5139	$27.51	$27.50	$27.50
Purchase #3	$203.85	6.424%	$216.9453	$216.95	$216.95	$216.90
Purchase #4	$31.97	5.742%	$33.8057	$33.81	$33.80	$33.80
Purchase #5	$230.51	3.307%	$238.133	$238.13	$238.15	$238.10
Purchase #6	$13.47	6.709%	$14.3737	$14.37	$14.35	$14.40
Purchase #7	$154.57	11.825%	$172.8479	$172.85	$172.85	$172.80
7 purchase totals =	$712.53		$761.0470	$761.05	$761.05	$760.90