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	$17.75	8.616%	$19.2793	$19.28	$19.30	$19.30
Purchase #2	$6.57	6.102%	$6.9709	$6.97	$6.95	$7.00
Purchase #3	$91.72	11.544%	$102.3082	$102.31	$102.30	$102.30
Purchase #4	$75.68	12.325%	$85.0076	$85.01	$85.00	$85.00
Purchase #5	$29.86	13.371%	$33.8526	$33.85	$33.85	$33.90
Purchase #6	$81.65	9.379%	$89.308	$89.31	$89.30	$89.30
Purchase #7	$114.33	4.191%	$119.1216	$119.12	$119.10	$119.10
7 purchase totals =	$417.56		$455.8482	$455.85	$455.80	$455.90