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	$39.68	10.382%	$43.7996	$43.80	$43.80	$43.80
Purchase #2	$79.80	11.553%	$89.0193	$89.02	$89.00	$89.00
Purchase #3	$105.46	6.188%	$111.9859	$111.99	$112.00	$112.00
Purchase #4	$54.27	13.639%	$61.6719	$61.67	$61.65	$61.70
Purchase #5	$78.40	7.635%	$84.3858	$84.39	$84.40	$84.40
Purchase #6	$35.85	13.327%	$40.6277	$40.63	$40.65	$40.60
Purchase #7	$30.99	4.747%	$32.4611	$32.46	$32.45	$32.50
7 purchase totals =	$424.45		$463.9513	$463.96	$463.95	$464.00