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	$156.84	3.807%	$162.8109	$162.81	$162.80	$162.80
Purchase #2	$81.38	9.349%	$88.9882	$88.99	$89.00	$89.00
Purchase #3	$244.70	3.149%	$252.4056	$252.41	$252.40	$252.40
Purchase #4	$41.56	8.509%	$45.0963	$45.10	$45.10	$45.10
Purchase #5	$133.72	3.448%	$138.3307	$138.33	$138.35	$138.30
Purchase #6	$164.45	9.355%	$179.8343	$179.83	$179.85	$179.80
Purchase #7	$180.94	8.503%	$196.3253	$196.33	$196.35	$196.30
7 purchase totals =	$1,003.59		$1,063.7913	$1,063.80	$1,063.85	$1,063.70