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	$75.88	12.859%	$85.6374	$85.64	$85.65	$85.60
Purchase #2	$240.82	12.560%	$271.067	$271.07	$271.05	$271.10
Purchase #3	$101.47	7.506%	$109.0863	$109.09	$109.10	$109.10
Purchase #4	$92.50	12.275%	$103.8544	$103.85	$103.85	$103.90
Purchase #5	$198.40	6.505%	$211.3059	$211.31	$211.30	$211.30
Purchase #6	$136.73	10.469%	$151.0443	$151.04	$151.05	$151.00
Purchase #7	$234.55	5.827%	$248.2172	$248.22	$248.20	$248.20
7 purchase totals =	$1,080.35		$1,180.2125	$1,180.22	$1,180.20	$1,180.20