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	$88.52	4.705%	$92.6849	$92.68	$92.70	$92.70
Purchase #2	$62.88	6.591%	$67.0244	$67.02	$67.00	$67.00
Purchase #3	$38.48	6.336%	$40.9181	$40.92	$40.90	$40.90
Purchase #4	$207.96	13.570%	$236.1802	$236.18	$236.20	$236.20
Purchase #5	$160.35	9.672%	$175.8591	$175.86	$175.85	$175.90
Purchase #6	$115.98	6.651%	$123.6938	$123.69	$123.70	$123.70
Purchase #7	$225.25	3.655%	$233.4829	$233.48	$233.50	$233.50
7 purchase totals =	$899.42		$969.8434	$969.83	$969.85	$969.90