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	$151.92	7.215%	$162.881	$162.88	$162.90	$162.90
Purchase #2	$41.54	6.351%	$44.1782	$44.18	$44.20	$44.20
Purchase #3	$139.29	13.735%	$158.4215	$158.42	$158.40	$158.40
Purchase #4	$82.54	12.300%	$92.6924	$92.69	$92.70	$92.70
Purchase #5	$39.82	7.860%	$42.9499	$42.95	$42.95	$42.90
Purchase #6	$131.90	9.122%	$143.9319	$143.93	$143.95	$143.90
Purchase #7	$181.99	4.552%	$190.2742	$190.27	$190.25	$190.30
7 purchase totals =	$769.00		$835.3291	$835.32	$835.35	$835.30