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	$47.44	10.726%	$52.5284	$52.53	$52.55	$52.50
Purchase #2	$118.97	5.227%	$125.1886	$125.19	$125.20	$125.20
Purchase #3	$9.53	5.698%	$10.073	$10.07	$10.05	$10.10
Purchase #4	$248.29	10.401%	$274.1146	$274.11	$274.10	$274.10
Purchase #5	$27.78	13.627%	$31.5656	$31.57	$31.55	$31.60
Purchase #6	$101.83	9.772%	$111.7808	$111.78	$111.80	$111.80
Purchase #7	$71.96	12.365%	$80.8579	$80.86	$80.85	$80.90
7 purchase totals =	$625.80		$686.1089	$686.11	$686.10	$686.20