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	$175.35	3.452%	$181.4031	$181.40	$181.40	$181.40
Purchase #2	$57.30	12.302%	$64.349	$64.35	$64.35	$64.30
Purchase #3	$242.98	12.456%	$273.2456	$273.25	$273.25	$273.20
Purchase #4	$179.54	11.336%	$199.8927	$199.89	$199.90	$199.90
Purchase #5	$136.61	6.519%	$145.5156	$145.52	$145.50	$145.50
Purchase #6	$47.30	11.844%	$52.9022	$52.90	$52.90	$52.90
Purchase #7	$43.82	10.213%	$48.2953	$48.30	$48.30	$48.30
7 purchase totals =	$882.90		$965.6035	$965.61	$965.60	$965.50