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	$155.53	11.215%	$172.9727	$172.97	$172.95	$173.00
Purchase #2	$215.84	13.618%	$245.2331	$245.23	$245.25	$245.20
Purchase #3	$89.45	7.265%	$95.9485	$95.95	$95.95	$95.90
Purchase #4	$61.91	8.742%	$67.3222	$67.32	$67.30	$67.30
Purchase #5	$185.39	7.496%	$199.2868	$199.29	$199.30	$199.30
Purchase #6	$16.41	13.394%	$18.608	$18.61	$18.60	$18.60
Purchase #7	$163.52	4.283%	$170.5236	$170.52	$170.50	$170.50
7 purchase totals =	$888.05		$969.8949	$969.89	$969.85	$969.80