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	$127.32	13.168%	$144.0855	$144.09	$144.10	$144.10
Purchase #2	$116.44	13.292%	$131.9172	$131.92	$131.90	$131.90
Purchase #3	$40.26	13.338%	$45.6299	$45.63	$45.65	$45.60
Purchase #4	$39.26	6.140%	$41.6706	$41.67	$41.65	$41.70
Purchase #5	$181.83	9.734%	$199.5293	$199.53	$199.55	$199.50
Purchase #6	$249.55	9.454%	$273.1425	$273.14	$273.15	$273.10
Purchase #7	$191.90	13.129%	$217.0946	$217.09	$217.10	$217.10
7 purchase totals =	$946.56		$1,053.0696	$1,053.07	$1,053.10	$1,053.00