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	$147.69	9.854%	$162.2434	$162.24	$162.25	$162.20
Purchase #2	$61.57	12.762%	$69.4276	$69.43	$69.45	$69.40
Purchase #3	$156.89	4.799%	$164.4192	$164.42	$164.40	$164.40
Purchase #4	$196.72	6.768%	$210.034	$210.03	$210.05	$210.00
Purchase #5	$25.46	11.254%	$28.3253	$28.33	$28.35	$28.30
Purchase #6	$181.63	7.128%	$194.5766	$194.58	$194.60	$194.60
Purchase #7	$76.26	12.593%	$85.8634	$85.86	$85.85	$85.90
7 purchase totals =	$846.22		$914.8895	$914.89	$914.95	$914.80