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	$230.30	3.805%	$239.0629	$239.06	$239.05	$239.10
Purchase #2	$51.57	7.836%	$55.611	$55.61	$55.60	$55.60
Purchase #3	$154.80	6.564%	$164.9611	$164.96	$164.95	$165.00
Purchase #4	$77.26	7.763%	$83.2577	$83.26	$83.25	$83.30
Purchase #5	$219.65	13.605%	$249.5334	$249.53	$249.55	$249.50
Purchase #6	$189.61	3.781%	$196.7792	$196.78	$196.80	$196.80
Purchase #7	$55.42	12.869%	$62.552	$62.55	$62.55	$62.60
7 purchase totals =	$978.61		$1,051.7573	$1,051.75	$1,051.75	$1,051.90