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	$112.55	13.130%	$127.3278	$127.33	$127.35	$127.30
Purchase #2	$154.46	11.311%	$171.931	$171.93	$171.95	$171.90
Purchase #3	$103.94	11.218%	$115.6	$115.60	$115.60	$115.60
Purchase #4	$19.42	4.202%	$20.236	$20.24	$20.25	$20.20
Purchase #5	$7.54	6.670%	$8.0429	$8.04	$8.05	$8.00
Purchase #6	$228.58	4.184%	$238.1438	$238.14	$238.15	$238.10
Purchase #7	$19.89	9.705%	$21.8203	$21.82	$21.80	$21.80
7 purchase totals =	$646.38		$703.1018	$703.10	$703.15	$702.90