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	$189.54	4.870%	$198.7706	$198.77	$198.75	$198.80
Purchase #2	$155.68	7.688%	$167.6487	$167.65	$167.65	$167.60
Purchase #3	$205.95	8.747%	$223.9644	$223.96	$223.95	$224.00
Purchase #4	$213.42	4.241%	$222.4711	$222.47	$222.45	$222.50
Purchase #5	$61.71	12.842%	$69.6348	$69.63	$69.65	$69.60
Purchase #6	$121.38	8.382%	$131.5541	$131.55	$131.55	$131.60
Purchase #7	$128.86	11.325%	$143.4534	$143.45	$143.45	$143.50
7 purchase totals =	$1,076.54		$1,157.4971	$1,157.48	$1,157.45	$1,157.60