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	$174.43	12.540%	$196.3035	$196.30	$196.30	$196.30
Purchase #2	$70.25	4.213%	$73.2096	$73.21	$73.20	$73.20
Purchase #3	$114.60	4.459%	$119.71	$119.71	$119.70	$119.70
Purchase #4	$104.30	10.397%	$115.1441	$115.14	$115.15	$115.10
Purchase #5	$225.55	6.364%	$239.904	$239.90	$239.90	$239.90
Purchase #6	$240.47	13.150%	$272.0918	$272.09	$272.10	$272.10
Purchase #7	$28.63	10.168%	$31.5411	$31.54	$31.55	$31.50
7 purchase totals =	$958.23		$1,047.9041	$1,047.89	$1,047.90	$1,047.80