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	$94.82	12.647%	$106.8119	$106.81	$106.80	$106.80
Purchase #2	$98.39	11.411%	$109.6173	$109.62	$109.60	$109.60
Purchase #3	$235.87	8.381%	$255.6383	$255.64	$255.65	$255.60
Purchase #4	$179.48	9.353%	$196.2668	$196.27	$196.25	$196.30
Purchase #5	$131.86	8.629%	$143.2382	$143.24	$143.25	$143.20
Purchase #6	$201.62	6.792%	$215.314	$215.31	$215.30	$215.30
Purchase #7	$153.66	9.397%	$168.0994	$168.10	$168.10	$168.10
7 purchase totals =	$1,095.70		$1,194.9859	$1,194.99	$1,194.95	$1,194.90