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	$152.59	6.477%	$162.4733	$162.47	$162.45	$162.50
Purchase #2	$163.70	9.871%	$179.8588	$179.86	$179.85	$179.90
Purchase #3	$91.36	12.504%	$102.7837	$102.78	$102.80	$102.80
Purchase #4	$103.48	7.555%	$111.2979	$111.30	$111.30	$111.30
Purchase #5	$6.50	7.487%	$6.9867	$6.99	$7.00	$7.00
Purchase #6	$69.48	3.521%	$71.9264	$71.93	$71.95	$71.90
Purchase #7	$243.33	7.486%	$261.5457	$261.55	$261.55	$261.50
7 purchase totals =	$830.44		$896.8725	$896.88	$896.90	$896.90