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	$176.56	3.381%	$182.5295	$182.53	$182.55	$182.50
Purchase #2	$230.79	3.184%	$238.1384	$238.14	$238.15	$238.10
Purchase #3	$175.86	5.741%	$185.9561	$185.96	$185.95	$186.00
Purchase #4	$85.44	6.263%	$90.7911	$90.79	$90.80	$90.80
Purchase #5	$105.99	10.272%	$116.8773	$116.88	$116.90	$116.90
Purchase #6	$131.32	9.709%	$144.0699	$144.07	$144.05	$144.10
Purchase #7	$110.88	11.203%	$123.3019	$123.30	$123.30	$123.30
7 purchase totals =	$1,016.84		$1,081.6642	$1,081.67	$1,081.70	$1,081.70