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	$221.63	4.517%	$231.641	$231.64	$231.65	$231.60
Purchase #2	$106.43	12.669%	$119.9136	$119.91	$119.90	$119.90
Purchase #3	$234.28	9.260%	$255.9743	$255.97	$255.95	$256.00
Purchase #4	$203.86	13.177%	$230.7226	$230.72	$230.70	$230.70
Purchase #5	$186.51	7.711%	$200.8918	$200.89	$200.90	$200.90
Purchase #6	$68.31	8.138%	$73.8691	$73.87	$73.85	$73.90
Purchase #7	$33.91	9.812%	$37.2372	$37.24	$37.25	$37.20
7 purchase totals =	$1,054.93		$1,150.2496	$1,150.24	$1,150.20	$1,150.20