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	$79.69	10.184%	$87.8056	$87.81	$87.80	$87.80
Purchase #2	$91.63	13.474%	$103.9762	$103.98	$104.00	$104.00
Purchase #3	$239.26	4.295%	$249.5362	$249.54	$249.55	$249.50
Purchase #4	$117.55	8.790%	$127.8826	$127.88	$127.90	$127.90
Purchase #5	$157.47	4.518%	$164.5845	$164.58	$164.60	$164.60
Purchase #6	$214.82	4.748%	$225.0197	$225.02	$225.00	$225.00
Purchase #7	$56.69	4.478%	$59.2286	$59.23	$59.25	$59.20
7 purchase totals =	$957.11		$1,018.0334	$1,018.04	$1,018.10	$1,018.00