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	$49.38	9.733%	$54.1862	$54.19	$54.20	$54.20
Purchase #2	$224.61	9.264%	$245.4179	$245.42	$245.40	$245.40
Purchase #3	$95.95	13.786%	$109.1777	$109.18	$109.20	$109.20
Purchase #4	$205.78	6.844%	$219.8636	$219.86	$219.85	$219.90
Purchase #5	$190.73	4.803%	$199.8908	$199.89	$199.90	$199.90
Purchase #6	$114.42	4.207%	$119.2336	$119.23	$119.25	$119.20
Purchase #7	$83.57	10.646%	$92.4669	$92.47	$92.45	$92.50
7 purchase totals =	$964.44		$1,040.2367	$1,040.24	$1,040.25	$1,040.30