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	$75.64	10.860%	$83.8545	$83.85	$83.85	$83.90
Purchase #2	$179.93	3.540%	$186.2995	$186.30	$186.30	$186.30
Purchase #3	$31.31	12.828%	$35.3264	$35.33	$35.35	$35.30
Purchase #4	$47.59	9.824%	$52.2652	$52.27	$52.25	$52.30
Purchase #5	$129.77	13.134%	$146.814	$146.81	$146.80	$146.80
Purchase #6	$222.26	7.297%	$238.4783	$238.48	$238.50	$238.50
Purchase #7	$189.99	3.492%	$196.6245	$196.62	$196.60	$196.60
7 purchase totals =	$876.49		$939.6624	$939.66	$939.65	$939.70