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	$93.44	8.801%	$101.6637	$101.66	$101.65	$101.70
Purchase #2	$56.72	12.502%	$63.8111	$63.81	$63.80	$63.80
Purchase #3	$89.93	6.345%	$95.6361	$95.64	$95.65	$95.60
Purchase #4	$221.35	3.447%	$228.9799	$228.98	$229.00	$229.00
Purchase #5	$249.49	12.535%	$280.7636	$280.76	$280.75	$280.80
Purchase #6	$187.46	9.526%	$205.3174	$205.32	$205.30	$205.30
Purchase #7	$101.59	9.490%	$111.2309	$111.23	$111.25	$111.20
7 purchase totals =	$999.98		$1,087.4027	$1,087.40	$1,087.40	$1,087.40