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	$67.88	7.393%	$72.8984	$72.90	$72.90	$72.90
Purchase #2	$80.96	10.828%	$89.7263	$89.73	$89.75	$89.70
Purchase #3	$181.68	4.846%	$190.4842	$190.48	$190.50	$190.50
Purchase #4	$127.67	3.531%	$132.178	$132.18	$132.20	$132.20
Purchase #5	$176.80	13.190%	$200.1199	$200.12	$200.10	$200.10
Purchase #6	$173.36	12.397%	$194.8514	$194.85	$194.85	$194.90
Purchase #7	$176.91	5.686%	$186.9691	$186.97	$186.95	$187.00
7 purchase totals =	$985.26		$1,067.2273	$1,067.23	$1,067.25	$1,067.30