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	$49.28	5.307%	$51.8953	$51.90	$51.90	$51.90
Purchase #2	$164.78	4.867%	$172.7998	$172.80	$172.80	$172.80
Purchase #3	$156.93	7.362%	$168.4832	$168.48	$168.50	$168.50
Purchase #4	$212.98	10.749%	$235.8732	$235.87	$235.85	$235.90
Purchase #5	$82.55	4.461%	$86.2326	$86.23	$86.25	$86.20
Purchase #6	$120.27	5.598%	$127.0027	$127.00	$127.00	$127.00
Purchase #7	$154.98	7.661%	$166.853	$166.85	$166.85	$166.90
7 purchase totals =	$941.77		$1,009.1398	$1,009.13	$1,009.15	$1,009.20