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	$74.50	10.648%	$82.4328	$82.43	$82.45	$82.40
Purchase #2	$189.87	5.736%	$200.7609	$200.76	$200.75	$200.80
Purchase #3	$149.45	4.567%	$156.2754	$156.28	$156.30	$156.30
Purchase #4	$117.92	11.582%	$131.5775	$131.58	$131.60	$131.60
Purchase #5	$142.73	10.775%	$158.1092	$158.11	$158.10	$158.10
Purchase #6	$87.92	5.636%	$92.8752	$92.88	$92.90	$92.90
Purchase #7	$201.69	12.790%	$227.4862	$227.49	$227.50	$227.50
7 purchase totals =	$964.08		$1,049.5172	$1,049.53	$1,049.60	$1,049.60