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	$167.58	5.163%	$176.2322	$176.23	$176.25	$176.20
Purchase #2	$186.79	5.378%	$196.8356	$196.84	$196.85	$196.80
Purchase #3	$35.87	12.184%	$40.2404	$40.24	$40.25	$40.20
Purchase #4	$41.88	12.609%	$47.1606	$47.16	$47.15	$47.20
Purchase #5	$31.98	6.623%	$34.098	$34.10	$34.10	$34.10
Purchase #6	$72.25	3.756%	$74.9637	$74.96	$74.95	$75.00
Purchase #7	$182.71	7.584%	$196.5667	$196.57	$196.55	$196.60
7 purchase totals =	$719.06		$766.0972	$766.10	$766.10	$766.10