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	$144.78	10.571%	$160.0847	$160.08	$160.10	$160.10
Purchase #2	$215.89	12.717%	$243.3447	$243.34	$243.35	$243.30
Purchase #3	$76.88	6.142%	$81.602	$81.60	$81.60	$81.60
Purchase #4	$84.32	6.176%	$89.5276	$89.53	$89.55	$89.50
Purchase #5	$167.66	4.290%	$174.8526	$174.85	$174.85	$174.90
Purchase #6	$108.83	4.601%	$113.8373	$113.84	$113.85	$113.80
Purchase #7	$134.33	3.133%	$138.5386	$138.54	$138.55	$138.50
7 purchase totals =	$932.69		$1,001.7875	$1,001.78	$1,001.85	$1,001.70