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	$214.37	12.560%	$241.2949	$241.29	$241.30	$241.30
Purchase #2	$41.74	9.587%	$45.7416	$45.74	$45.75	$45.70
Purchase #3	$65.51	6.854%	$70.0001	$70.00	$70.00	$70.00
Purchase #4	$86.51	11.485%	$96.4457	$96.45	$96.45	$96.40
Purchase #5	$78.93	7.813%	$85.0968	$85.10	$85.10	$85.10
Purchase #6	$250.46	12.761%	$282.4212	$282.42	$282.40	$282.40
Purchase #7	$179.99	8.800%	$195.8291	$195.83	$195.85	$195.80
7 purchase totals =	$917.51		$1,016.8294	$1,016.83	$1,016.85	$1,016.70