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	$139.47	7.690%	$150.1952	$150.20	$150.20	$150.20
Purchase #2	$109.79	8.480%	$119.1002	$119.10	$119.10	$119.10
Purchase #3	$74.78	10.664%	$82.7545	$82.75	$82.75	$82.80
Purchase #4	$220.33	6.833%	$235.3851	$235.39	$235.40	$235.40
Purchase #5	$63.72	5.329%	$67.1156	$67.12	$67.10	$67.10
Purchase #6	$124.70	5.791%	$131.9214	$131.92	$131.90	$131.90
Purchase #7	$170.85	11.543%	$190.5712	$190.57	$190.55	$190.60
7 purchase totals =	$903.64		$977.0432	$977.05	$977.00	$977.10