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	$171.96	10.745%	$190.4371	$190.44	$190.45	$190.40
Purchase #2	$227.85	7.275%	$244.4261	$244.43	$244.45	$244.40
Purchase #3	$113.46	11.742%	$126.7825	$126.78	$126.80	$126.80
Purchase #4	$89.43	3.245%	$92.332	$92.33	$92.35	$92.30
Purchase #5	$164.81	3.763%	$171.0118	$171.01	$171.00	$171.00
Purchase #6	$131.97	6.194%	$140.1442	$140.14	$140.15	$140.10
Purchase #7	$35.78	13.492%	$40.6074	$40.61	$40.60	$40.60
7 purchase totals =	$935.26		$1,005.7411	$1,005.74	$1,005.80	$1,005.60