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	$47.65	13.801%	$54.2262	$54.23	$54.25	$54.20
Purchase #2	$218.31	8.769%	$237.4536	$237.45	$237.45	$237.50
Purchase #3	$82.37	11.635%	$91.9537	$91.95	$91.95	$92.00
Purchase #4	$233.97	12.625%	$263.5087	$263.51	$263.50	$263.50
Purchase #5	$150.80	12.622%	$169.834	$169.83	$169.85	$169.80
Purchase #6	$210.40	12.424%	$236.5401	$236.54	$236.55	$236.50
Purchase #7	$132.62	8.111%	$143.3768	$143.38	$143.40	$143.40
7 purchase totals =	$1,076.12		$1,196.8931	$1,196.89	$1,196.95	$1,196.90