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	$160.59	4.278%	$167.46	$167.46	$167.45	$167.50
Purchase #2	$100.37	13.330%	$113.7493	$113.75	$113.75	$113.70
Purchase #3	$195.83	12.450%	$220.2108	$220.21	$220.20	$220.20
Purchase #4	$176.86	8.116%	$191.214	$191.21	$191.20	$191.20
Purchase #5	$165.52	4.404%	$172.8095	$172.81	$172.80	$172.80
Purchase #6	$124.93	5.243%	$131.4801	$131.48	$131.50	$131.50
Purchase #7	$230.78	7.455%	$247.9846	$247.98	$248.00	$248.00
7 purchase totals =	$1,154.88		$1,244.9083	$1,244.90	$1,244.90	$1,244.90