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	$47.36	3.728%	$49.1256	$49.13	$49.15	$49.10
Purchase #2	$127.97	7.131%	$137.0955	$137.10	$137.10	$137.10
Purchase #3	$132.49	5.381%	$139.6193	$139.62	$139.60	$139.60
Purchase #4	$238.76	10.613%	$264.0996	$264.10	$264.10	$264.10
Purchase #5	$212.51	12.263%	$238.5701	$238.57	$238.55	$238.60
Purchase #6	$96.36	7.363%	$103.455	$103.46	$103.45	$103.50
Purchase #7	$73.29	6.737%	$78.2275	$78.23	$78.25	$78.20
7 purchase totals =	$928.74		$1,010.1926	$1,010.21	$1,010.20	$1,010.20