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	$201.26	4.135%	$209.5821	$209.58	$209.60	$209.60
Purchase #2	$88.99	9.666%	$97.5918	$97.59	$97.60	$97.60
Purchase #3	$202.69	6.123%	$215.1007	$215.10	$215.10	$215.10
Purchase #4	$178.89	3.156%	$184.5358	$184.54	$184.55	$184.50
Purchase #5	$250.94	4.284%	$261.6903	$261.69	$261.70	$261.70
Purchase #6	$125.86	13.185%	$142.4546	$142.45	$142.45	$142.50
Purchase #7	$129.50	11.250%	$144.0688	$144.07	$144.05	$144.10
7 purchase totals =	$1,178.13		$1,255.0241	$1,255.02	$1,255.05	$1,255.10