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	$169.70	9.765%	$186.2712	$186.27	$186.25	$186.30
Purchase #2	$234.42	9.142%	$255.8507	$255.85	$255.85	$255.90
Purchase #3	$32.88	3.702%	$34.0972	$34.10	$34.10	$34.10
Purchase #4	$151.72	10.651%	$167.8797	$167.88	$167.90	$167.90
Purchase #5	$141.80	8.523%	$153.8856	$153.89	$153.90	$153.90
Purchase #6	$240.91	9.820%	$264.5674	$264.57	$264.55	$264.60
Purchase #7	$244.79	6.755%	$261.3256	$261.33	$261.35	$261.30
7 purchase totals =	$1,216.22		$1,323.8774	$1,323.89	$1,323.90	$1,324.00