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	$176.63	8.343%	$191.3662	$191.37	$191.35	$191.40
Purchase #2	$192.64	8.142%	$208.3247	$208.32	$208.30	$208.30
Purchase #3	$114.31	8.380%	$123.8892	$123.89	$123.90	$123.90
Purchase #4	$76.54	10.653%	$84.6938	$84.69	$84.70	$84.70
Purchase #5	$56.52	9.598%	$61.9448	$61.94	$61.95	$61.90
Purchase #6	$190.39	8.471%	$206.5179	$206.52	$206.50	$206.50
Purchase #7	$168.75	3.678%	$174.9566	$174.96	$174.95	$175.00
7 purchase totals =	$975.78		$1,051.6932	$1,051.69	$1,051.65	$1,051.70