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	$205.60	7.860%	$221.7602	$221.76	$221.75	$221.80
Purchase #2	$157.28	4.667%	$164.6203	$164.62	$164.60	$164.60
Purchase #3	$67.72	13.172%	$76.6401	$76.64	$76.65	$76.60
Purchase #4	$105.29	12.477%	$118.427	$118.43	$118.45	$118.40
Purchase #5	$197.86	6.611%	$210.9405	$210.94	$210.95	$210.90
Purchase #6	$167.65	13.341%	$190.0162	$190.02	$190.00	$190.00
Purchase #7	$78.60	7.153%	$84.2223	$84.22	$84.20	$84.20
7 purchase totals =	$980.00		$1,066.6266	$1,066.63	$1,066.60	$1,066.50