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	$54.52	8.854%	$59.3472	$59.35	$59.35	$59.30
Purchase #2	$87.64	11.633%	$97.8352	$97.84	$97.85	$97.80
Purchase #3	$130.46	11.290%	$145.1889	$145.19	$145.20	$145.20
Purchase #4	$168.50	10.362%	$185.96	$185.96	$185.95	$186.00
Purchase #5	$82.65	4.495%	$86.3651	$86.37	$86.35	$86.40
Purchase #6	$53.68	5.179%	$56.4601	$56.46	$56.45	$56.50
Purchase #7	$102.88	9.201%	$112.346	$112.35	$112.35	$112.30
7 purchase totals =	$680.33		$743.5025	$743.52	$743.50	$743.50