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	$245.62	12.273%	$275.7649	$275.76	$275.75	$275.80
Purchase #2	$42.51	3.266%	$43.8984	$43.90	$43.90	$43.90
Purchase #3	$43.94	3.454%	$45.4577	$45.46	$45.45	$45.50
Purchase #4	$77.75	3.372%	$80.3717	$80.37	$80.35	$80.40
Purchase #5	$133.86	8.196%	$144.8312	$144.83	$144.85	$144.80
Purchase #6	$167.42	3.357%	$173.0403	$173.04	$173.05	$173.00
Purchase #7	$5.62	6.342%	$5.9764	$5.98	$6.00	$6.00
7 purchase totals =	$716.72		$769.3406	$769.34	$769.35	$769.40