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	$174.85	12.359%	$196.4597	$196.46	$196.45	$196.50
Purchase #2	$120.88	8.291%	$130.9022	$130.90	$130.90	$130.90
Purchase #3	$18.59	5.125%	$19.5427	$19.54	$19.55	$19.50
Purchase #4	$122.96	4.698%	$128.7367	$128.74	$128.75	$128.70
Purchase #5	$176.71	12.455%	$198.7192	$198.72	$198.70	$198.70
Purchase #6	$45.74	13.701%	$52.0068	$52.01	$52.00	$52.00
Purchase #7	$137.46	11.421%	$153.1593	$153.16	$153.15	$153.20
7 purchase totals =	$797.19		$879.5266	$879.53	$879.50	$879.50