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	$143.42	12.721%	$161.6645	$161.66	$161.65	$161.70
Purchase #2	$45.83	10.111%	$50.4639	$50.46	$50.45	$50.50
Purchase #3	$215.78	11.807%	$241.2571	$241.26	$241.25	$241.30
Purchase #4	$156.68	3.858%	$162.7247	$162.72	$162.70	$162.70
Purchase #5	$54.29	3.299%	$56.081	$56.08	$56.10	$56.10
Purchase #6	$212.59	3.706%	$220.4686	$220.47	$220.45	$220.50
Purchase #7	$149.30	11.133%	$165.9216	$165.92	$165.90	$165.90
7 purchase totals =	$977.89		$1,058.5814	$1,058.57	$1,058.50	$1,058.70