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	$180.33	10.551%	$199.3566	$199.36	$199.35	$199.40
Purchase #2	$218.83	4.471%	$228.6139	$228.61	$228.60	$228.60
Purchase #3	$113.77	6.176%	$120.7964	$120.80	$120.80	$120.80
Purchase #4	$123.71	13.482%	$140.3886	$140.39	$140.40	$140.40
Purchase #5	$81.75	4.592%	$85.504	$85.50	$85.50	$85.50
Purchase #6	$224.73	12.754%	$253.3921	$253.39	$253.40	$253.40
Purchase #7	$85.70	12.308%	$96.248	$96.25	$96.25	$96.20
7 purchase totals =	$1,028.82		$1,124.2996	$1,124.30	$1,124.30	$1,124.30