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	$241.50	3.464%	$249.8656	$249.87	$249.85	$249.90
Purchase #2	$162.34	10.731%	$179.7607	$179.76	$179.75	$179.80
Purchase #3	$125.95	12.676%	$141.9154	$141.92	$141.90	$141.90
Purchase #4	$198.25	3.479%	$205.1471	$205.15	$205.15	$205.10
Purchase #5	$82.56	3.141%	$85.1532	$85.15	$85.15	$85.20
Purchase #6	$138.75	10.161%	$152.8484	$152.85	$152.85	$152.80
Purchase #7	$114.93	6.658%	$122.582	$122.58	$122.60	$122.60
7 purchase totals =	$1,064.28		$1,137.2724	$1,137.28	$1,137.25	$1,137.30