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	$215.58	10.493%	$238.2008	$238.20	$238.20	$238.20
Purchase #2	$169.60	3.271%	$175.1476	$175.15	$175.15	$175.10
Purchase #3	$119.76	7.599%	$128.8606	$128.86	$128.85	$128.90
Purchase #4	$153.41	11.560%	$171.1442	$171.14	$171.15	$171.10
Purchase #5	$154.75	8.176%	$167.4024	$167.40	$167.40	$167.40
Purchase #6	$243.78	12.187%	$273.4895	$273.49	$273.50	$273.50
Purchase #7	$73.39	12.558%	$82.6063	$82.61	$82.60	$82.60
7 purchase totals =	$1,130.27		$1,236.8514	$1,236.85	$1,236.85	$1,236.80