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	$8.82	11.643%	$9.8469	$9.85	$9.85	$9.80
Purchase #2	$35.61	7.416%	$38.2508	$38.25	$38.25	$38.30
Purchase #3	$59.25	9.389%	$64.813	$64.81	$64.80	$64.80
Purchase #4	$95.40	3.677%	$98.9079	$98.91	$98.90	$98.90
Purchase #5	$62.77	4.372%	$65.5143	$65.51	$65.50	$65.50
Purchase #6	$208.63	3.215%	$215.3375	$215.34	$215.35	$215.30
Purchase #7	$179.83	5.413%	$189.5642	$189.56	$189.55	$189.60
7 purchase totals =	$650.31		$682.2346	$682.23	$682.20	$682.20