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	$131.30	9.871%	$144.2606	$144.26	$144.25	$144.30
Purchase #2	$100.98	12.487%	$113.5894	$113.59	$113.60	$113.60
Purchase #3	$199.92	6.314%	$212.5429	$212.54	$212.55	$212.50
Purchase #4	$39.64	4.222%	$41.3136	$41.31	$41.30	$41.30
Purchase #5	$247.34	12.567%	$278.4232	$278.42	$278.40	$278.40
Purchase #6	$102.27	12.193%	$114.7398	$114.74	$114.75	$114.70
Purchase #7	$243.31	6.657%	$259.5071	$259.51	$259.50	$259.50
7 purchase totals =	$1,064.76		$1,164.3766	$1,164.37	$1,164.35	$1,164.30