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	$66.90	7.575%	$71.9677	$71.97	$71.95	$72.00
Purchase #2	$41.59	3.848%	$43.1904	$43.19	$43.20	$43.20
Purchase #3	$34.76	7.765%	$37.4591	$37.46	$37.45	$37.50
Purchase #4	$69.84	3.541%	$72.313	$72.31	$72.30	$72.30
Purchase #5	$21.76	7.791%	$23.4553	$23.46	$23.45	$23.50
Purchase #6	$109.69	10.185%	$120.8619	$120.86	$120.85	$120.90
Purchase #7	$177.68	9.592%	$194.7231	$194.72	$194.70	$194.70
7 purchase totals =	$522.22		$563.9705	$563.97	$563.90	$564.10