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	$143.81	12.861%	$162.3054	$162.31	$162.30	$162.30
Purchase #2	$231.84	12.624%	$261.1075	$261.11	$261.10	$261.10
Purchase #3	$99.37	7.619%	$106.941	$106.94	$106.95	$106.90
Purchase #4	$211.53	9.343%	$231.2932	$231.29	$231.30	$231.30
Purchase #5	$92.58	8.694%	$100.6289	$100.63	$100.65	$100.60
Purchase #6	$42.38	12.143%	$47.5262	$47.53	$47.55	$47.50
Purchase #7	$98.86	13.116%	$111.8265	$111.83	$111.85	$111.80
7 purchase totals =	$920.37		$1,021.6287	$1,021.64	$1,021.70	$1,021.50