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	$176.27	11.440%	$196.4353	$196.44	$196.45	$196.40
Purchase #2	$48.46	3.531%	$50.1711	$50.17	$50.15	$50.20
Purchase #3	$152.44	11.771%	$170.3837	$170.38	$170.40	$170.40
Purchase #4	$116.25	3.262%	$120.0421	$120.04	$120.05	$120.00
Purchase #5	$237.56	10.473%	$262.4397	$262.44	$262.45	$262.40
Purchase #6	$23.79	5.671%	$25.1391	$25.14	$25.15	$25.10
Purchase #7	$162.61	11.837%	$181.8581	$181.86	$181.85	$181.90
7 purchase totals =	$917.38		$1,006.4691	$1,006.47	$1,006.50	$1,006.40