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	$218.91	4.123%	$227.9357	$227.94	$227.95	$227.90
Purchase #2	$86.86	10.470%	$95.9542	$95.95	$95.95	$96.00
Purchase #3	$209.68	9.493%	$229.5849	$229.58	$229.60	$229.60
Purchase #4	$130.67	9.356%	$142.8955	$142.90	$142.90	$142.90
Purchase #5	$233.35	10.746%	$258.4258	$258.43	$258.45	$258.40
Purchase #6	$179.30	3.197%	$185.0322	$185.03	$185.05	$185.00
Purchase #7	$52.72	7.133%	$56.4805	$56.48	$56.50	$56.50
7 purchase totals =	$1,111.49		$1,196.3088	$1,196.31	$1,196.40	$1,196.30