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	$68.59	3.637%	$71.0846	$71.08	$71.10	$71.10
Purchase #2	$138.90	9.622%	$152.265	$152.27	$152.25	$152.30
Purchase #3	$145.64	6.531%	$155.1517	$155.15	$155.15	$155.20
Purchase #4	$148.25	3.416%	$153.3142	$153.31	$153.30	$153.30
Purchase #5	$161.30	6.203%	$171.3054	$171.31	$171.30	$171.30
Purchase #6	$189.36	5.625%	$200.0115	$200.01	$200.00	$200.00
Purchase #7	$33.82	10.317%	$37.3092	$37.31	$37.30	$37.30
7 purchase totals =	$885.86		$940.4416	$940.44	$940.40	$940.50