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	$135.29	3.435%	$139.9372	$139.94	$139.95	$139.90
Purchase #2	$149.82	4.573%	$156.6713	$156.67	$156.65	$156.70
Purchase #3	$189.53	3.788%	$196.7094	$196.71	$196.70	$196.70
Purchase #4	$161.75	7.426%	$173.7616	$173.76	$173.75	$173.80
Purchase #5	$51.51	4.299%	$53.7244	$53.72	$53.70	$53.70
Purchase #6	$42.89	11.188%	$47.6885	$47.69	$47.70	$47.70
Purchase #7	$241.30	5.558%	$254.7115	$254.71	$254.70	$254.70
7 purchase totals =	$972.09		$1,023.2039	$1,023.20	$1,023.15	$1,023.20