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	$220.85	11.200%	$245.5852	$245.59	$245.60	$245.60
Purchase #2	$81.60	6.285%	$86.7286	$86.73	$86.75	$86.70
Purchase #3	$231.45	6.698%	$246.9525	$246.95	$246.95	$247.00
Purchase #4	$46.42	6.700%	$49.5301	$49.53	$49.55	$49.50
Purchase #5	$25.52	6.189%	$27.0994	$27.10	$27.10	$27.10
Purchase #6	$57.41	4.263%	$59.8574	$59.86	$59.85	$59.90
Purchase #7	$82.44	9.474%	$90.2504	$90.25	$90.25	$90.30
7 purchase totals =	$745.69		$806.0036	$806.01	$806.05	$806.10