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	$194.82	10.340%	$214.9644	$214.96	$214.95	$215.00
Purchase #2	$101.88	7.621%	$109.6443	$109.64	$109.65	$109.60
Purchase #3	$123.81	12.706%	$139.5413	$139.54	$139.55	$139.50
Purchase #4	$97.53	6.311%	$103.6851	$103.69	$103.70	$103.70
Purchase #5	$7.43	6.275%	$7.8962	$7.90	$7.90	$7.90
Purchase #6	$153.45	11.496%	$171.0906	$171.09	$171.10	$171.10
Purchase #7	$175.94	7.386%	$188.9349	$188.93	$188.95	$188.90
7 purchase totals =	$854.86		$935.7568	$935.75	$935.80	$935.70