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	$57.93	3.330%	$59.8591	$59.86	$59.85	$59.90
Purchase #2	$200.58	12.738%	$226.1299	$226.13	$226.15	$226.10
Purchase #3	$187.83	5.759%	$198.6471	$198.65	$198.65	$198.60
Purchase #4	$158.61	12.296%	$178.1127	$178.11	$178.10	$178.10
Purchase #5	$83.48	7.375%	$89.6367	$89.64	$89.65	$89.60
Purchase #6	$157.29	10.197%	$173.3289	$173.33	$173.35	$173.30
Purchase #7	$211.34	7.108%	$226.362	$226.36	$226.35	$226.40
7 purchase totals =	$1,057.06		$1,152.0764	$1,152.08	$1,152.10	$1,152.00