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	$199.65	11.496%	$222.6018	$222.60	$222.60	$222.60
Purchase #2	$65.92	12.124%	$73.9121	$73.91	$73.90	$73.90
Purchase #3	$112.91	7.538%	$121.4212	$121.42	$121.40	$121.40
Purchase #4	$150.43	9.194%	$164.2605	$164.26	$164.25	$164.30
Purchase #5	$118.67	10.702%	$131.3701	$131.37	$131.35	$131.40
Purchase #6	$212.88	4.402%	$222.251	$222.25	$222.25	$222.30
Purchase #7	$54.40	9.494%	$59.5647	$59.56	$59.55	$59.60
7 purchase totals =	$914.86		$995.3814	$995.37	$995.30	$995.50