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	$30.71	8.549%	$33.3354	$33.34	$33.35	$33.30
Purchase #2	$49.33	9.122%	$53.8299	$53.83	$53.85	$53.80
Purchase #3	$163.95	8.516%	$177.912	$177.91	$177.90	$177.90
Purchase #4	$98.61	4.600%	$103.1461	$103.15	$103.15	$103.10
Purchase #5	$33.93	11.812%	$37.9378	$37.94	$37.95	$37.90
Purchase #6	$60.54	3.538%	$62.6819	$62.68	$62.70	$62.70
Purchase #7	$222.90	12.398%	$250.5351	$250.54	$250.55	$250.50
7 purchase totals =	$659.97		$719.3782	$719.39	$719.45	$719.20