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	$196.48	10.274%	$216.6664	$216.67	$216.65	$216.70
Purchase #2	$187.95	12.735%	$211.8854	$211.89	$211.90	$211.90
Purchase #3	$248.84	8.296%	$269.4838	$269.48	$269.50	$269.50
Purchase #4	$141.55	6.635%	$150.9418	$150.94	$150.95	$150.90
Purchase #5	$30.29	7.399%	$32.5312	$32.53	$32.55	$32.50
Purchase #6	$187.67	4.627%	$196.3535	$196.35	$196.35	$196.40
Purchase #7	$164.77	3.869%	$171.145	$171.15	$171.15	$171.10
7 purchase totals =	$1,157.55		$1,249.0071	$1,249.01	$1,249.05	$1,249.00