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	$201.83	5.228%	$212.3817	$212.38	$212.40	$212.40
Purchase #2	$89.25	10.260%	$98.4071	$98.41	$98.40	$98.40
Purchase #3	$100.85	6.694%	$107.6009	$107.60	$107.60	$107.60
Purchase #4	$215.89	3.682%	$223.8391	$223.84	$223.85	$223.80
Purchase #5	$82.80	9.217%	$90.4317	$90.43	$90.45	$90.40
Purchase #6	$206.70	10.371%	$228.1369	$228.14	$228.15	$228.10
Purchase #7	$51.28	7.112%	$54.927	$54.93	$54.95	$54.90
7 purchase totals =	$948.60		$1,015.7244	$1,015.73	$1,015.80	$1,015.60