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	$156.73	4.689%	$164.0791	$164.08	$164.10	$164.10
Purchase #2	$99.97	3.352%	$103.321	$103.32	$103.30	$103.30
Purchase #3	$52.89	5.792%	$55.9534	$55.95	$55.95	$56.00
Purchase #4	$42.52	10.747%	$47.0896	$47.09	$47.10	$47.10
Purchase #5	$72.51	5.243%	$76.3117	$76.31	$76.30	$76.30
Purchase #6	$46.35	10.217%	$51.0856	$51.09	$51.10	$51.10
Purchase #7	$202.34	3.780%	$209.9885	$209.99	$210.00	$210.00
7 purchase totals =	$673.31		$707.8289	$707.83	$707.85	$707.90