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	$202.85	4.696%	$212.3758	$212.38	$212.40	$212.40
Purchase #2	$36.79	4.698%	$38.5184	$38.52	$38.50	$38.50
Purchase #3	$54.75	12.314%	$61.4919	$61.49	$61.50	$61.50
Purchase #4	$219.63	4.113%	$228.6634	$228.66	$228.65	$228.70
Purchase #5	$11.29	9.119%	$12.3195	$12.32	$12.30	$12.30
Purchase #6	$131.43	3.498%	$136.0274	$136.03	$136.05	$136.00
Purchase #7	$174.48	4.779%	$182.8184	$182.82	$182.80	$182.80
7 purchase totals =	$831.22		$872.2148	$872.22	$872.20	$872.20