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	$158.51	8.104%	$171.3557	$171.36	$171.35	$171.40
Purchase #2	$33.28	13.636%	$37.8181	$37.82	$37.80	$37.80
Purchase #3	$199.55	13.703%	$226.8943	$226.89	$226.90	$226.90
Purchase #4	$221.89	10.249%	$244.6315	$244.63	$244.65	$244.60
Purchase #5	$199.66	11.336%	$222.2935	$222.29	$222.30	$222.30
Purchase #6	$106.79	8.421%	$115.7828	$115.78	$115.80	$115.80
Purchase #7	$142.88	13.145%	$161.6616	$161.66	$161.65	$161.70
7 purchase totals =	$1,062.56		$1,180.4375	$1,180.43	$1,180.45	$1,180.50