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	$200.93	6.430%	$213.8498	$213.85	$213.85	$213.80
Purchase #2	$36.77	7.714%	$39.6064	$39.61	$39.60	$39.60
Purchase #3	$181.44	8.509%	$196.8787	$196.88	$196.90	$196.90
Purchase #4	$31.82	3.272%	$32.8612	$32.86	$32.85	$32.90
Purchase #5	$41.82	4.160%	$43.5597	$43.56	$43.55	$43.60
Purchase #6	$170.41	11.566%	$190.1196	$190.12	$190.10	$190.10
Purchase #7	$233.26	12.803%	$263.1243	$263.12	$263.10	$263.10
7 purchase totals =	$896.45		$979.9997	$980.00	$979.95	$980.00