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	$137.68	11.476%	$153.4802	$153.48	$153.50	$153.50
Purchase #2	$115.86	9.798%	$127.212	$127.21	$127.20	$127.20
Purchase #3	$141.35	7.775%	$152.34	$152.34	$152.35	$152.30
Purchase #4	$125.51	13.789%	$142.8166	$142.82	$142.80	$142.80
Purchase #5	$92.40	7.495%	$99.3254	$99.33	$99.35	$99.30
Purchase #6	$195.58	6.240%	$207.7842	$207.78	$207.80	$207.80
Purchase #7	$159.35	10.535%	$176.1375	$176.14	$176.15	$176.10
7 purchase totals =	$967.73		$1,059.0959	$1,059.10	$1,059.15	$1,059.00