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	$54.38	9.466%	$59.5276	$59.53	$59.55	$59.50
Purchase #2	$10.88	4.351%	$11.3534	$11.35	$11.35	$11.40
Purchase #3	$171.47	12.278%	$192.5231	$192.52	$192.50	$192.50
Purchase #4	$234.82	3.249%	$242.4493	$242.45	$242.45	$242.40
Purchase #5	$180.26	3.321%	$186.2464	$186.25	$186.25	$186.20
Purchase #6	$80.43	7.253%	$86.2636	$86.26	$86.25	$86.30
Purchase #7	$58.92	11.550%	$65.7253	$65.73	$65.75	$65.70
7 purchase totals =	$791.16		$844.0887	$844.09	$844.10	$844.00