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	$111.90	9.389%	$122.4063	$122.41	$122.40	$122.40
Purchase #2	$195.36	13.360%	$221.4601	$221.46	$221.45	$221.50
Purchase #3	$72.43	11.774%	$80.9579	$80.96	$80.95	$81.00
Purchase #4	$250.66	11.855%	$280.3757	$280.38	$280.40	$280.40
Purchase #5	$101.84	3.106%	$105.0032	$105.00	$105.00	$105.00
Purchase #6	$105.32	5.629%	$111.2485	$111.25	$111.25	$111.20
Purchase #7	$130.42	12.500%	$146.7225	$146.72	$146.70	$146.70
7 purchase totals =	$967.93		$1,068.1742	$1,068.18	$1,068.15	$1,068.20