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	$138.99	5.731%	$146.9555	$146.96	$146.95	$147.00
Purchase #2	$135.42	12.689%	$152.6034	$152.60	$152.60	$152.60
Purchase #3	$59.68	9.869%	$65.5698	$65.57	$65.55	$65.60
Purchase #4	$96.60	4.192%	$100.6495	$100.65	$100.65	$100.60
Purchase #5	$130.72	9.252%	$142.8142	$142.81	$142.80	$142.80
Purchase #6	$232.86	12.284%	$261.4645	$261.46	$261.45	$261.50
Purchase #7	$224.73	9.592%	$246.2861	$246.29	$246.30	$246.30
7 purchase totals =	$1,019.00		$1,116.3430	$1,116.34	$1,116.30	$1,116.40