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	$53.86	3.166%	$55.5652	$55.57	$55.55	$55.60
Purchase #2	$86.38	3.417%	$89.3316	$89.33	$89.35	$89.30
Purchase #3	$124.94	9.787%	$137.1679	$137.17	$137.15	$137.20
Purchase #4	$160.51	8.660%	$174.4102	$174.41	$174.40	$174.40
Purchase #5	$208.61	13.774%	$237.3439	$237.34	$237.35	$237.30
Purchase #6	$177.37	4.213%	$184.8426	$184.84	$184.85	$184.80
Purchase #7	$250.75	13.236%	$283.9393	$283.94	$283.95	$283.90
7 purchase totals =	$1,062.42		$1,162.6007	$1,162.60	$1,162.60	$1,162.50