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	$18.86	4.161%	$19.6448	$19.64	$19.65	$19.60
Purchase #2	$238.39	8.674%	$259.0679	$259.07	$259.05	$259.10
Purchase #3	$80.97	12.241%	$90.8815	$90.88	$90.90	$90.90
Purchase #4	$187.71	11.367%	$209.047	$209.05	$209.05	$209.00
Purchase #5	$79.41	12.739%	$89.526	$89.53	$89.55	$89.50
Purchase #6	$215.86	11.257%	$240.1594	$240.16	$240.15	$240.20
Purchase #7	$63.94	7.472%	$68.7176	$68.72	$68.70	$68.70
7 purchase totals =	$885.14		$977.0442	$977.05	$977.05	$977.00