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	$212.85	13.855%	$242.3404	$242.34	$242.35	$242.30
Purchase #2	$34.91	5.711%	$36.9037	$36.90	$36.90	$36.90
Purchase #3	$47.38	11.728%	$52.9367	$52.94	$52.95	$52.90
Purchase #4	$99.63	12.302%	$111.8865	$111.89	$111.90	$111.90
Purchase #5	$92.77	11.486%	$103.4256	$103.43	$103.45	$103.40
Purchase #6	$82.30	3.822%	$85.4455	$85.45	$85.45	$85.40
Purchase #7	$143.69	10.565%	$158.8708	$158.87	$158.85	$158.90
7 purchase totals =	$713.53		$791.8092	$791.82	$791.85	$791.70