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	$125.44	13.317%	$142.1448	$142.14	$142.15	$142.10
Purchase #2	$147.94	13.657%	$168.1442	$168.14	$168.15	$168.10
Purchase #3	$101.34	4.186%	$105.5821	$105.58	$105.60	$105.60
Purchase #4	$63.74	9.752%	$69.9559	$69.96	$69.95	$70.00
Purchase #5	$166.39	3.851%	$172.7977	$172.80	$172.80	$172.80
Purchase #6	$201.31	12.111%	$225.6907	$225.69	$225.70	$225.70
Purchase #7	$113.90	9.649%	$124.8902	$124.89	$124.90	$124.90
7 purchase totals =	$920.06		$1,009.2056	$1,009.20	$1,009.25	$1,009.20