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	$128.76	9.501%	$140.9935	$140.99	$141.00	$141.00
Purchase #2	$237.26	7.142%	$254.2051	$254.21	$254.20	$254.20
Purchase #3	$115.94	10.735%	$128.3862	$128.39	$128.40	$128.40
Purchase #4	$104.78	6.465%	$111.554	$111.55	$111.55	$111.60
Purchase #5	$154.78	7.733%	$166.7491	$166.75	$166.75	$166.70
Purchase #6	$205.81	5.706%	$217.5535	$217.55	$217.55	$217.60
Purchase #7	$85.41	5.481%	$90.0913	$90.09	$90.10	$90.10
7 purchase totals =	$1,032.74		$1,109.5327	$1,109.53	$1,109.55	$1,109.60