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	$134.38	7.418%	$144.3483	$144.35	$144.35	$144.30
Purchase #2	$239.63	7.213%	$256.9145	$256.91	$256.90	$256.90
Purchase #3	$38.86	11.351%	$43.271	$43.27	$43.25	$43.30
Purchase #4	$108.28	5.715%	$114.4682	$114.47	$114.45	$114.50
Purchase #5	$177.85	12.809%	$200.6308	$200.63	$200.65	$200.60
Purchase #6	$211.47	7.135%	$226.5584	$226.56	$226.55	$226.60
Purchase #7	$186.39	10.376%	$205.7298	$205.73	$205.75	$205.70
7 purchase totals =	$1,096.86		$1,191.9210	$1,191.92	$1,191.90	$1,191.90