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	$215.89	9.559%	$236.5269	$236.53	$236.55	$236.50
Purchase #2	$47.86	9.657%	$52.4818	$52.48	$52.50	$52.50
Purchase #3	$192.51	6.750%	$205.5044	$205.50	$205.50	$205.50
Purchase #4	$106.33	10.490%	$117.484	$117.48	$117.50	$117.50
Purchase #5	$90.96	10.677%	$100.6718	$100.67	$100.65	$100.70
Purchase #6	$94.71	8.735%	$102.9829	$102.98	$103.00	$103.00
Purchase #7	$236.81	10.521%	$261.7248	$261.72	$261.70	$261.70
7 purchase totals =	$985.07		$1,077.3766	$1,077.36	$1,077.40	$1,077.40