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	$243.81	3.266%	$251.7728	$251.77	$251.75	$251.80
Purchase #2	$108.30	13.853%	$123.3028	$123.30	$123.30	$123.30
Purchase #3	$71.76	9.710%	$78.7279	$78.73	$78.75	$78.70
Purchase #4	$67.65	8.749%	$73.5687	$73.57	$73.55	$73.60
Purchase #5	$61.93	7.660%	$66.6738	$66.67	$66.65	$66.70
Purchase #6	$166.46	6.298%	$176.9437	$176.94	$176.95	$176.90
Purchase #7	$234.58	4.462%	$245.047	$245.05	$245.05	$245.00
7 purchase totals =	$954.49		$1,016.0367	$1,016.03	$1,016.00	$1,016.00