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	$131.42	4.637%	$137.5139	$137.51	$137.50	$137.50
Purchase #2	$38.63	11.797%	$43.1872	$43.19	$43.20	$43.20
Purchase #3	$135.50	11.117%	$150.5635	$150.56	$150.55	$150.60
Purchase #4	$103.30	8.833%	$112.4245	$112.42	$112.40	$112.40
Purchase #5	$159.97	8.804%	$174.0538	$174.05	$174.05	$174.10
Purchase #6	$190.72	10.404%	$210.5625	$210.56	$210.55	$210.60
Purchase #7	$190.50	3.448%	$197.0684	$197.07	$197.05	$197.10
7 purchase totals =	$950.04		$1,025.3738	$1,025.36	$1,025.30	$1,025.50