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	$96.90	5.274%	$102.0105	$102.01	$102.00	$102.00
Purchase #2	$226.58	12.667%	$255.2809	$255.28	$255.30	$255.30
Purchase #3	$186.93	9.564%	$204.808	$204.81	$204.80	$204.80
Purchase #4	$135.35	12.123%	$151.7585	$151.76	$151.75	$151.80
Purchase #5	$156.82	9.559%	$171.8104	$171.81	$171.80	$171.80
Purchase #6	$170.95	8.382%	$185.279	$185.28	$185.30	$185.30
Purchase #7	$13.25	6.216%	$14.0736	$14.07	$14.05	$14.10
7 purchase totals =	$986.78		$1,085.0209	$1,085.02	$1,085.00	$1,085.10