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	$152.98	13.659%	$173.8755	$173.88	$173.90	$173.90
Purchase #2	$83.57	3.546%	$86.5334	$86.53	$86.55	$86.50
Purchase #3	$161.81	8.871%	$176.1642	$176.16	$176.15	$176.20
Purchase #4	$224.27	9.815%	$246.2821	$246.28	$246.30	$246.30
Purchase #5	$199.38	4.499%	$208.3501	$208.35	$208.35	$208.40
Purchase #6	$121.38	5.156%	$127.6384	$127.64	$127.65	$127.60
Purchase #7	$141.39	7.769%	$152.3746	$152.37	$152.35	$152.40
7 purchase totals =	$1,084.78		$1,171.2183	$1,171.21	$1,171.25	$1,171.30