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	$184.83	13.538%	$209.8523	$209.85	$209.85	$209.90
Purchase #2	$78.92	11.325%	$87.8577	$87.86	$87.85	$87.90
Purchase #3	$25.53	6.152%	$27.1006	$27.10	$27.10	$27.10
Purchase #4	$86.87	4.289%	$90.5959	$90.60	$90.60	$90.60
Purchase #5	$113.75	6.290%	$120.9049	$120.90	$120.90	$120.90
Purchase #6	$181.87	3.149%	$187.5971	$187.60	$187.60	$187.60
Purchase #7	$155.67	4.248%	$162.2829	$162.28	$162.30	$162.30
7 purchase totals =	$827.44		$886.1914	$886.19	$886.20	$886.30