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	$109.84	3.462%	$113.6427	$113.64	$113.65	$113.60
Purchase #2	$213.81	9.856%	$234.8831	$234.88	$234.90	$234.90
Purchase #3	$202.76	11.861%	$226.8094	$226.81	$226.80	$226.80
Purchase #4	$78.94	12.873%	$89.1019	$89.10	$89.10	$89.10
Purchase #5	$95.43	3.272%	$98.5525	$98.55	$98.55	$98.60
Purchase #6	$222.63	8.501%	$241.5558	$241.56	$241.55	$241.60
Purchase #7	$41.63	4.607%	$43.5479	$43.55	$43.55	$43.50
7 purchase totals =	$965.04		$1,048.0933	$1,048.09	$1,048.10	$1,048.10