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	$211.96	4.529%	$221.5597	$221.56	$221.55	$221.60
Purchase #2	$168.90	10.815%	$187.1665	$187.17	$187.15	$187.20
Purchase #3	$229.40	13.613%	$260.6282	$260.63	$260.65	$260.60
Purchase #4	$228.46	9.249%	$249.5903	$249.59	$249.60	$249.60
Purchase #5	$41.85	4.780%	$43.8504	$43.85	$43.85	$43.90
Purchase #6	$43.83	5.115%	$46.0719	$46.07	$46.05	$46.10
Purchase #7	$111.40	9.656%	$122.1568	$122.16	$122.15	$122.20
7 purchase totals =	$1,035.80		$1,131.0238	$1,131.03	$1,131.00	$1,131.20