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	$204.29	10.379%	$225.4933	$225.49	$225.50	$225.50
Purchase #2	$142.67	3.269%	$147.3339	$147.33	$147.35	$147.30
Purchase #3	$214.85	4.461%	$224.4345	$224.43	$224.45	$224.40
Purchase #4	$192.83	3.860%	$200.2732	$200.27	$200.25	$200.30
Purchase #5	$151.95	7.201%	$162.8919	$162.89	$162.90	$162.90
Purchase #6	$64.74	4.469%	$67.6332	$67.63	$67.65	$67.60
Purchase #7	$231.84	3.299%	$239.4884	$239.49	$239.50	$239.50
7 purchase totals =	$1,203.17		$1,267.5484	$1,267.53	$1,267.60	$1,267.50