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	$71.58	9.762%	$78.5676	$78.57	$78.55	$78.60
Purchase #2	$104.73	11.842%	$117.1321	$117.13	$117.15	$117.10
Purchase #3	$10.94	9.617%	$11.9921	$11.99	$12.00	$12.00
Purchase #4	$62.63	12.290%	$70.3272	$70.33	$70.35	$70.30
Purchase #5	$20.56	9.714%	$22.5572	$22.56	$22.55	$22.60
Purchase #6	$132.52	7.723%	$142.7545	$142.75	$142.75	$142.80
Purchase #7	$113.89	12.439%	$128.0568	$128.06	$128.05	$128.10
7 purchase totals =	$516.85		$571.3875	$571.39	$571.40	$571.50