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	$168.88	7.864%	$182.1607	$182.16	$182.15	$182.20
Purchase #2	$169.57	6.273%	$180.2071	$180.21	$180.20	$180.20
Purchase #3	$226.72	10.521%	$250.5732	$250.57	$250.55	$250.60
Purchase #4	$157.33	4.516%	$164.435	$164.44	$164.45	$164.40
Purchase #5	$132.94	7.845%	$143.3691	$143.37	$143.35	$143.40
Purchase #6	$142.86	13.748%	$162.5004	$162.50	$162.50	$162.50
Purchase #7	$59.82	4.601%	$62.5723	$62.57	$62.55	$62.60
7 purchase totals =	$1,058.12		$1,145.8178	$1,145.82	$1,145.75	$1,145.90