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	$145.79	11.259%	$162.2045	$162.20	$162.20	$162.20
Purchase #2	$37.39	3.752%	$38.7929	$38.79	$38.80	$38.80
Purchase #3	$224.38	9.447%	$245.5772	$245.58	$245.60	$245.60
Purchase #4	$199.75	4.403%	$208.545	$208.55	$208.55	$208.50
Purchase #5	$101.52	8.192%	$109.8365	$109.84	$109.85	$109.80
Purchase #6	$80.78	6.201%	$85.7892	$85.79	$85.80	$85.80
Purchase #7	$205.36	12.525%	$231.0813	$231.08	$231.10	$231.10
7 purchase totals =	$994.97		$1,081.8266	$1,081.83	$1,081.90	$1,081.80