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	$141.71	6.369%	$150.7355	$150.74	$150.75	$150.70
Purchase #2	$90.78	8.330%	$98.342	$98.34	$98.35	$98.30
Purchase #3	$86.61	11.837%	$96.862	$96.86	$96.85	$96.90
Purchase #4	$118.32	8.264%	$128.098	$128.10	$128.10	$128.10
Purchase #5	$55.72	13.679%	$63.3419	$63.34	$63.35	$63.30
Purchase #6	$50.29	11.300%	$55.9728	$55.97	$55.95	$56.00
Purchase #7	$132.81	6.865%	$141.9274	$141.93	$141.95	$141.90
7 purchase totals =	$676.24		$735.2796	$735.28	$735.30	$735.20