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	$208.32	8.394%	$225.8064	$225.81	$225.80	$225.80
Purchase #2	$182.62	9.771%	$200.4638	$200.46	$200.45	$200.50
Purchase #3	$154.38	6.768%	$164.8284	$164.83	$164.85	$164.80
Purchase #4	$8.31	7.266%	$8.9138	$8.91	$8.90	$8.90
Purchase #5	$145.59	10.181%	$160.4125	$160.41	$160.40	$160.40
Purchase #6	$205.80	13.442%	$233.4636	$233.46	$233.45	$233.50
Purchase #7	$167.84	13.502%	$190.5018	$190.50	$190.50	$190.50
7 purchase totals =	$1,072.86		$1,184.3903	$1,184.38	$1,184.35	$1,184.40