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	$211.42	6.341%	$224.8261	$224.83	$224.85	$224.80
Purchase #2	$151.38	10.858%	$167.8168	$167.82	$167.80	$167.80
Purchase #3	$171.72	6.348%	$182.6208	$182.62	$182.60	$182.60
Purchase #4	$50.37	9.139%	$54.9733	$54.97	$54.95	$55.00
Purchase #5	$97.60	3.800%	$101.3088	$101.31	$101.30	$101.30
Purchase #6	$9.67	13.862%	$11.0105	$11.01	$11.00	$11.00
Purchase #7	$246.43	9.345%	$269.4589	$269.46	$269.45	$269.50
7 purchase totals =	$938.59		$1,012.0152	$1,012.02	$1,011.95	$1,012.00