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	$182.69	4.371%	$190.6754	$190.68	$190.70	$190.70
Purchase #2	$227.53	10.112%	$250.5378	$250.54	$250.55	$250.50
Purchase #3	$109.96	12.474%	$123.6764	$123.68	$123.70	$123.70
Purchase #4	$230.43	3.638%	$238.813	$238.81	$238.80	$238.80
Purchase #5	$181.63	4.531%	$189.8597	$189.86	$189.85	$189.90
Purchase #6	$117.82	13.194%	$133.3652	$133.37	$133.35	$133.40
Purchase #7	$150.50	7.414%	$161.6581	$161.66	$161.65	$161.70
7 purchase totals =	$1,200.56		$1,288.5856	$1,288.60	$1,288.60	$1,288.70