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	$191.70	12.175%	$215.0395	$215.04	$215.05	$215.00
Purchase #2	$249.97	5.735%	$264.3058	$264.31	$264.30	$264.30
Purchase #3	$72.83	4.649%	$76.2159	$76.22	$76.20	$76.20
Purchase #4	$44.40	7.238%	$47.6137	$47.61	$47.60	$47.60
Purchase #5	$144.97	6.602%	$154.5409	$154.54	$154.55	$154.50
Purchase #6	$48.32	12.337%	$54.2812	$54.28	$54.30	$54.30
Purchase #7	$163.69	13.200%	$185.2971	$185.30	$185.30	$185.30
7 purchase totals =	$915.88		$997.2941	$997.30	$997.30	$997.20