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	$115.65	3.285%	$119.4491	$119.45	$119.45	$119.40
Purchase #2	$228.27	12.430%	$256.644	$256.64	$256.65	$256.60
Purchase #3	$186.84	5.181%	$196.5202	$196.52	$196.50	$196.50
Purchase #4	$185.36	13.745%	$210.8377	$210.84	$210.85	$210.80
Purchase #5	$82.59	13.102%	$93.4109	$93.41	$93.40	$93.40
Purchase #6	$226.60	6.523%	$241.3811	$241.38	$241.40	$241.40
Purchase #7	$189.49	13.492%	$215.056	$215.06	$215.05	$215.10
7 purchase totals =	$1,214.80		$1,333.2990	$1,333.30	$1,333.30	$1,333.20