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	$208.66	9.664%	$228.8249	$228.82	$228.80	$228.80
Purchase #2	$169.32	9.802%	$185.9167	$185.92	$185.90	$185.90
Purchase #3	$87.68	10.258%	$96.6742	$96.67	$96.65	$96.70
Purchase #4	$89.48	10.256%	$98.6571	$98.66	$98.65	$98.70
Purchase #5	$10.78	3.390%	$11.1454	$11.15	$11.15	$11.10
Purchase #6	$72.40	8.572%	$78.6061	$78.61	$78.60	$78.60
Purchase #7	$69.55	10.497%	$76.8507	$76.85	$76.85	$76.90
7 purchase totals =	$707.87		$776.6751	$776.68	$776.60	$776.70