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	$111.29	7.705%	$119.8649	$119.86	$119.85	$119.90
Purchase #2	$183.39	9.530%	$200.8671	$200.87	$200.85	$200.90
Purchase #3	$247.52	6.832%	$264.4306	$264.43	$264.45	$264.40
Purchase #4	$141.67	8.752%	$154.069	$154.07	$154.05	$154.10
Purchase #5	$78.75	11.843%	$88.0764	$88.08	$88.10	$88.10
Purchase #6	$150.73	11.493%	$168.0534	$168.05	$168.05	$168.10
Purchase #7	$71.87	9.305%	$78.5575	$78.56	$78.55	$78.60
7 purchase totals =	$985.22		$1,073.9189	$1,073.92	$1,073.90	$1,074.10