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	$106.86	7.481%	$114.8542	$114.85	$114.85	$114.90
Purchase #2	$164.49	10.807%	$182.2664	$182.27	$182.25	$182.30
Purchase #3	$103.77	9.341%	$113.4632	$113.46	$113.45	$113.50
Purchase #4	$23.28	9.287%	$25.442	$25.44	$25.45	$25.40
Purchase #5	$243.76	11.347%	$271.4194	$271.42	$271.40	$271.40
Purchase #6	$156.78	6.360%	$166.7512	$166.75	$166.75	$166.80
Purchase #7	$92.61	12.527%	$104.2113	$104.21	$104.20	$104.20
7 purchase totals =	$891.55		$978.4077	$978.40	$978.35	$978.50