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	$129.57	4.835%	$135.8347	$135.83	$135.85	$135.80
Purchase #2	$240.84	7.316%	$258.4599	$258.46	$258.45	$258.50
Purchase #3	$162.59	8.560%	$176.5077	$176.51	$176.50	$176.50
Purchase #4	$54.92	13.438%	$62.3001	$62.30	$62.30	$62.30
Purchase #5	$205.31	9.493%	$224.8001	$224.80	$224.80	$224.80
Purchase #6	$107.39	6.317%	$114.1738	$114.17	$114.15	$114.20
Purchase #7	$79.42	12.543%	$89.3817	$89.38	$89.40	$89.40
7 purchase totals =	$980.04		$1,061.4580	$1,061.45	$1,061.45	$1,061.50